NPException generated when accessing Context on ftl freemarker

[Bora_]

Hi. I have created a document template using freemarker. How can i get the properties of parent of the current doc. I can use the session to get what i want, but the context doesn`t work properly, it causes error.

<center>
<img src=${Env['nuxeo.url']}/img/stema_republikes.jpg" height="7%" width="5%"/>
<p style="font-weight:bold;font-size: 12pt;font-family: "Times New Roman", Times, serif;">REPUBLIKA E SHQIPËRISË</br>MINISTRIA E DREJTËSISË</br>Drejtoria e Përgjithshme e Burgjeve</p>
</center>
<hr style="height:20px; color:black"/>
    <p style="float: right; width: 50%; text-align: right;font-size: 12pt;font-family: "Times New Roman", Times, serif;">Afati i Ruajtjes __ vit</br>Kopje nr. ___</p>
</br></br>
<center>
<p><span  style="font-weight:bold;font-family: "Times New Roman", Times, serif;">URDHËR TRANSFERIMI</span>
</br>Nr.__________ Datë ${CurrentDate.format("dd.MM.yyyy")}</p>
</center>

<p> ${Document["vendime:numer"]}</br>
${Document.id}</br>
${doc['vendime:numer']}</br>
${session.getRepositoryName()}</br>
${context.getClass()}</br>
</p>........etc

[Bora_]

${Context['param_name']}