Unhandled Error!

Trying to get property of non-object

Document	Product Page
Document type	CMS template
Line	2
Exception class	Cms_ExecutionException

Code Highlight

<? $this->render_partial('header') ?>
<? $categories = $product->category_list[0]->get_parents(true) ?>
<body class="<?= $categories[0]->code ?>">
<div class="container">
    <div id="header">
      <div id="top-nav">
        <div class="inner">
          <a class="secure" style="float: left; margin: 0 5px 2px 0;" href="http://verify.authorize.net/anetseal/?pid=101694e2-d3ce-4e05-b355-e0d5136fb07e&rurl=http%3A//www.blackarrowindianart.com/"><img width="60px" height="" src="<?= root_url('/resources/css/authorize2.png') ?>" /></a>	
          <p style="float: left; margin-right: 5px;">Secure Verified Merchant</a></p>
          <p>| Questions? <a href="<?= root_url('/contact-us') ?>">Contact Us</a></p>
          <? $this->render_partial('tabs') ?>
        </div>
      </div>

#	Document	Type
1	Product Page	CMS template