#009306: fetch content class_attribute makes a fatal error

Operating System: GNU/Debian
PHP Version: (please be specific, like '4.4.3' or '5.1.5') 4.4.2
Database and version: MySQL 4.1

{let attribute_sel=fetch('content', 'class_attribute', hash('attribute_id', 268))}
{$attribute_sel|attribute(show, 2)}
{/let}
produce :
Fatal error: Call to a member function on a non-object in /home/damien/public_html/ipev/kernel/classes/ezcontentobjectattribute.php on line 392
Fatal error: eZ publish did not finish its request

The execution of eZ publish was abruptly ended, the debug output is present below.