Even if it's a bad practice deleting users from a site we can sometimes delete some user by mistake... And if this happens, and we don't have a way to bring it back (for instance) we will start having an error in the logs every time we navigate in our content tree:

[ Nov 07 2012 12:19:49 ] [127.0.0.1] eZContentObject::attribute:
Attribute 'creator_id' does not exist

This error is shown because the "creator_id" attribute is being fetched in the wrong way.
The bug seems to be on line 263 in extension/ezjscore/classes/ezjscajaxcontent.php

                $ret['creator'] = array( 'id'   => $contentObject->attribute( 'creator_id' ),
                                         'name' => null );// user has been deleted

The correct fetch to the 'creator_id' attribute should be something like this:

                $ret['creator'] = array( 'id'   => $contentObject->attribute( 'current' )->attribute('creator_id'),
                                         'name' => null );// user has been deleted

Steps to Reproduce:

• Create an editor user.
• With the new editor user create a folder under /Home
• delete the editor user
• visit the root node on site_admin
• in the logs there will be an error message like:
  [ Nov 07 2012 12:19:49 ] [127.0.0.1] eZContentObject::attribute:
  Attribute 'creator_id' does not exist

With the proposed solution the error isn't shown anymore.