Unhandled Error!

Trying to get property of non-object

Document	product_breadcrumb
Document type	CMS partial
Line	5
Exception class	Cms_ExecutionException

Code Highlight

<div id="breadcrumb">
  <ul>
     <li><a href="" title="Home">Home</a><span>&raquo;</span></li>
    <?
$product_category = $product->category_list[0];
$parent_categories  = array();
$parent = $product_category ;
 
while ($parent = $parent->get_parent())
    $parent_categories[] = $parent;
 
// Print the category path
  foreach ($parent_categories as $category){

#	Document	Type
2	product_breadcrumb	CMS partial
1	products	CMS template