Caused by: freemarker.core.InvalidReferenceException: The following has evaluated to null or missing:

[karuppasamy]

Caused by: org.alfresco.service.cmr.repository.TemplateException: 02010171 Error during processing of the template 'The following has evaluated to nul
l or missing:
==> clientdata [in template "it/iopenway/emsmcrefund-getClient.get.json.ftl" at line 1, column 9]

Tip: If the failing expression is known to be legally null/missing, either specify a default value with myOptionalVar!myDefault, or use <#if myOptiona
lVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthessis: (myO
ptionVar.foo)!myDefault, (myOptionVar.foo)??

The failing instruction:
==> #list clientdata as clientdata [in template "it/iopenway/emsmcrefund-getClient.get.json.ftl" at line 1, column 2]'. Please contact your system ad
ministrator.
at org.alfresco.repo.template.FreeMarkerProcessor.process(FreeMarkerProcessor.java:234)
at org.springframework.extensions.webscripts.AbstractWebScript.renderTemplate(AbstractWebScript.java:967)
at org.springframework.extensions.webscripts.DeclarativeWebScript.renderFormatTemplate(DeclarativeWebScript.java:267)
at org.springframework.extensions.webscripts.DeclarativeWebScript.execute(DeclarativeWebScript.java:147)
... 37 more
Caused by: freemarker.core.InvalidReferenceException: The following has evaluated to null or missing:
==> clientdata [in template "it/iopenway/emsmcrefund-getClient.get.json.ftl" at line 1, column 9]

Tip: If the failing expression is known to be legally null/missing, either specify a default value with myOptionalVar!myDefault, or use <#if myOptiona
lVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthessis: (myO
ptionVar.foo)!myDefault, (myOptionVar.foo)??

The failing instruction:
==> #list clientdata as clientdata [in template "it/iopenway/emsmcrefund-getClient.get.json.ftl" at line 1, column 2]
at freemarker.core.InvalidReferenceException.getInstance(InvalidReferenceException.java:98)
at freemarker.core.Expression.assertNonNull(Expression.java:205)
at freemarker.core.IteratorBlock.accept(IteratorBlock.java:100)
at freemarker.core.Environment.visit(Environment.java:265)
at freemarker.core.MixedContent.accept(MixedContent.java:93)
at freemarker.core.Environment.visit(Environment.java:265)
at freemarker.core.Environment.process(Environment.java:243)
at org.alfresco.repo.template.FreeMarkerProcessor.process(FreeMarkerProcessor.java:230)
... 40 more
2019-03-01 10:52:40,514 ERROR [extensions.webscripts.AbstractRuntime] [http-apr-8080-exec-1] Exception from executeScript: 02010038 Wrapped Exception
(with status template): 02010170 Error during processing of the template 'The following has evaluated to null or missing:
==> dataas [in template "it/iopenway/emsmcrefund-getAddressStatus.get.json.ftl" at line 1, column 9]

Tip: If the failing expression is known to be legally null/missing, either specify a default value with myOptionalVar!myDefault, or use <#if myOptiona
lVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthessis: (myO
ptionVar.foo)!myDefault, (myOptionVar.foo)??

The failing instruction:
==> #list dataas as dataas [in template "it/iopenway/emsmcrefund-getAddressStatus.get.json.ftl" at line 1, column 2]'. Please contact your system adm
inistrator.
org.springframework.extensions.webscripts.WebScriptException: 02010038 Wrapped Exception (with status template): 02010170 Error during processing of
the template 'The following has evaluated to null or missing:
==> dataas [in template "it/iopenway/emsmcrefund-getAddressStatus.get.json.ftl" at line 1, column 9]

Tip: If the failing expression is known to be legally null/missing, either specify a default value with myOptionalVar!myDefault, or use <#if myOptiona
lVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthessis: (myO
ptionVar.foo)!myDefault, (myOptionVar.foo)??

The failing instruction:
==> #list dataas as dataas [in template "it/iopenway/emsmcrefund-getAddressStatus.get.json.ftl" at line 1, column 2]'. Please contact your system adm
inistrator.
at org.springframework.extensions.webscripts.AbstractWebScript.createStatusException(AbstractWebScript.java:1138)
at org.springframework.extensions.webscripts.DeclarativeWebScript.execute(DeclarativeWebScript.java:171)
at org.alfresco.repo.web.scripts.RepositoryContainer$3.execute(RepositoryContainer.java:519)
at org.alfresco.repo.transaction.RetryingTransactionHelper.doInTransaction(RetryingTransactionHelper.java:464)
at org.alfresco.repo.web.scripts.RepositoryContainer.transactionedExecute(RepositoryContainer.java:587)
at org.alfresco.repo.web.scripts.RepositoryContainer.transactionedExecuteAs(RepositoryContainer.java:656)
at org.alfresco.repo.web.scripts.RepositoryContainer.executeScriptInternal(RepositoryContainer.java:428)
at org.alfresco.repo.web.scripts.RepositoryContainer.executeScript(RepositoryContainer.java:308)
at org.springframework.extensions.webscripts.AbstractRuntime.executeScript(AbstractRuntime.java:399)
at org.springframework.extensions.webscripts.AbstractRuntime.executeScript(AbstractRuntime.java:210)
at org.springframework.extensions.webscripts.servlet.WebScriptServlet.service(WebScriptServlet.java:132)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.alfresco.module.aosmodule.service.ContextRootFilter.doFilter(ContextRootFilter.java:93)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.alfresco.web.app.servlet.GlobalLocalizationFilter.doFilter(GlobalLocalizationFilter.java:68)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:218)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:110)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:506)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:962)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:445)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1115)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:637)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2549)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2538)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Unknown Source)
Caused by: org.alfresco.service.cmr.repository.TemplateException: 02010170 Error during processing of the template 'The following has evaluated to nul
l or missing:
==> dataas [in template "it/iopenway/emsmcrefund-getAddressStatus.get.json.ftl" at line 1, column 9]

Tip: If the failing expression is known to be legally null/missing, either specify a default value with myOptionalVar!myDefault, or use <#if myOptiona
lVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthessis: (myO
ptionVar.foo)!myDefault, (myOptionVar.foo)??

The failing instruction:
==> #list dataas as dataas [in template "it/iopenway/emsmcrefund-getAddressStatus.get.json.ftl" at line 1, column 2]'. Please contact your system adm
inistrator.
at org.alfresco.repo.template.FreeMarkerProcessor.process(FreeMarkerProcessor.java:234)
at org.springframework.extensions.webscripts.AbstractWebScript.renderTemplate(AbstractWebScript.java:967)
at org.springframework.extensions.webscripts.DeclarativeWebScript.renderFormatTemplate(DeclarativeWebScript.java:267)
at org.springframework.extensions.webscripts.DeclarativeWebScript.execute(DeclarativeWebScript.java:147)
... 37 more
Caused by: freemarker.core.InvalidReferenceException: The following has evaluated to null or missing:
==> dataas [in template "it/iopenway/emsmcrefund-getAddressStatus.get.json.ftl" at line 1, column 9]

Tip: If the failing expression is known to be legally null/missing, either specify a default value with myOptionalVar!myDefault, or use <#if myOptiona
lVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthessis: (myO
ptionVar.foo)!myDefault, (myOptionVar.foo)??

The failing instruction:
==> #list dataas as dataas [in template "it/iopenway/emsmcrefund-getAddressStatus.get.json.ftl" at line 1, column 2]
at freemarker.core.InvalidReferenceException.getInstance(InvalidReferenceException.java:98)
at freemarker.core.Expression.assertNonNull(Expression.java:205)
at freemarker.core.IteratorBlock.accept(IteratorBlock.java:100)
at freemarker.core.Environment.visit(Environment.java:265)
at freemarker.core.MixedContent.accept(MixedContent.java:93)
at freemarker.core.Environment.visit(Environment.java:265)
at freemarker.core.Environment.process(Environment.java:243)
at org.alfresco.repo.template.FreeMarkerProcessor.process(FreeMarkerProcessor.java:230)
... 40 more
2019-03-01 10:52:40,494 ERROR [extensions.webscripts.AbstractRuntime] [http-apr-8080-exec-17] Exception from executeScript: 02010037 Wrapped Exceptio
n (with status template): 02010169 Error during processing of the template 'The following has evaluated to null or missing:
==> datapn [in template "it/iopenway/emsmcrefund-getPayerName.get.json.ftl" at line 1, column 9]

Tip: If the failing expression is known to be legally null/missing, either specify a default value with myOptionalVar!myDefault, or use <#if myOptiona
lVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthessis: (myO
ptionVar.foo)!myDefault, (myOptionVar.foo)??

The failing instruction:
==> #list datapn as datapn [in template "it/iopenway/emsmcrefund-getPayerName.get.json.ftl" at line 1, column 2]'. Please contact your system adminis
trator.
org.springframework.extensions.webscripts.WebScriptException: 02010037 Wrapped Exception (with status template): 02010169 Error during processing of
the template 'The following has evaluated to null or missing:
==> datapn [in template "it/iopenway/emsmcrefund-getPayerName.get.json.ftl" at line 1, column 9]

Tip: If the failing expression is known to be legally null/missing, either specify a default value with myOptionalVar!myDefault, or use <#if myOptiona
lVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthessis: (myO
ptionVar.foo)!myDefault, (myOptionVar.foo)??

The failing instruction:
==> #list datapn as datapn [in template "it/iopenway/emsmcrefund-getPayerName.get.json.ftl" at line 1, column 2]'. Please contact your system adminis
trator.
at org.springframework.extensions.webscripts.AbstractWebScript.createStatusException(AbstractWebScript.java:1138)
at org.springframework.extensions.webscripts.DeclarativeWebScript.execute(DeclarativeWebScript.java:171)
at org.alfresco.repo.web.scripts.RepositoryContainer$3.execute(RepositoryContainer.java:519)
at org.alfresco.repo.transaction.RetryingTransactionHelper.doInTransaction(RetryingTransactionHelper.java:464)
at org.alfresco.repo.web.scripts.RepositoryContainer.transactionedExecute(RepositoryContainer.java:587)
at org.alfresco.repo.web.scripts.RepositoryContainer.transactionedExecuteAs(RepositoryContainer.java:656)
at org.alfresco.repo.web.scripts.RepositoryContainer.executeScriptInternal(RepositoryContainer.java:428)
at org.alfresco.repo.web.scripts.RepositoryContainer.executeScript(RepositoryContainer.java:308)
at org.springframework.extensions.webscripts.AbstractRuntime.executeScript(AbstractRuntime.java:399)
at org.springframework.extensions.webscripts.AbstractRuntime.executeScript(AbstractRuntime.java:210)
at org.springframework.extensions.webscripts.servlet.WebScriptServlet.service(WebScriptServlet.java:132)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.alfresco.module.aosmodule.service.ContextRootFilter.doFilter(ContextRootFilter.java:93)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.alfresco.web.app.servlet.GlobalLocalizationFilter.doFilter(GlobalLocalizationFilter.java:68)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:218)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:110)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:506)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:962)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:445)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1115)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:637)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2549)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2538)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Unknown Source)
Caused by: org.alfresco.service.cmr.repository.TemplateException: 02010169 Error during processing of the template 'The following has evaluated to nul
l or missing:
==> datapn [in template "it/iopenway/emsmcrefund-getPayerName.get.json.ftl" at line 1, column 9]

Tip: If the failing expression is known to be legally null/missing, either specify a default value with myOptionalVar!myDefault, or use <#if myOptiona
lVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthessis: (myO
ptionVar.foo)!myDefault, (myOptionVar.foo)??

The failing instruction:
==> #list datapn as datapn [in template "it/iopenway/emsmcrefund-getPayerName.get.json.ftl" at line 1, column 2]'. Please contact your system adminis
trator.
at org.alfresco.repo.template.FreeMarkerProcessor.process(FreeMarkerProcessor.java:234)
at org.springframework.extensions.webscripts.AbstractWebScript.renderTemplate(AbstractWebScript.java:967)
at org.springframework.extensions.webscripts.DeclarativeWebScript.renderFormatTemplate(DeclarativeWebScript.java:267)
at org.springframework.extensions.webscripts.DeclarativeWebScript.execute(DeclarativeWebScript.java:147)
... 37 more
Caused by: freemarker.core.InvalidReferenceException: The following has evaluated to null or missing:
==> datapn [in template "it/iopenway/emsmcrefund-getPayerName.get.json.ftl" at line 1, column 9]

Tip: If the failing expression is known to be legally null/missing, either specify a default value with myOptionalVar!myDefault, or use <#if myOptiona
lVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthessis: (myO
ptionVar.foo)!myDefault, (myOptionVar.foo)??

The failing instruction:
==> #list datapn as datapn [in template "it/iopenway/emsmcrefund-getPayerName.get.json.ftl" at line 1, column 2]
at freemarker.core.InvalidReferenceException.getInstance(InvalidReferenceException.java:98)
at freemarker.core.Expression.assertNonNull(Expression.java:205)
at freemarker.core.IteratorBlock.accept(IteratorBlock.java:100)
at freemarker.core.Environment.visit(Environment.java:265)
at freemarker.core.MixedContent.accept(MixedContent.java:93)
at freemarker.core.Environment.visit(Environment.java:265)
at freemarker.core.Environment.process(Environment.java:243)
at org.alfresco.repo.template.FreeMarkerProcessor.process(FreeMarkerProcessor.java:230)
... 40 more

[jpotts]

As the stack trace indicates, your variables (clientdata, datapn, dataas) are null. You should do a null check in your freemarker template to avoid accessing a null variable.

As you have only provided a stack trace and no other context or code, I really can't help you further.