Index: branches/5.1.x/core/kernel/db/cat_event_handler.php
===================================================================
diff -u -N -r14321 -r14443
--- branches/5.1.x/core/kernel/db/cat_event_handler.php	(.../cat_event_handler.php)	(revision 14321)
+++ branches/5.1.x/core/kernel/db/cat_event_handler.php	(.../cat_event_handler.php)	(revision 14443)
@@ -1,6 +1,6 @@
 <?php
 /**
-* @version	$Id: cat_event_handler.php 14321 2011-05-20 08:00:19Z alex $
+* @version	$Id: cat_event_handler.php 14443 2011-07-08 10:11:10Z alex $
 * @package	In-Portal
 * @copyright	Copyright (C) 1997 - 2009 Intechnic. All rights reserved.
 * @license      GNU/GPL
@@ -957,9 +957,11 @@
 			$file_helper->LoadItemFiles($object);
 		}
 
-		// set item's additional categories to virtual field (used in editing)
-		$item_categories = $this->getItemCategories($object->GetDBField('ResourceId'));
-		$object->SetDBField('MoreCategories', $item_categories ? '|'.implode('|', $item_categories).'|' : '');
+		if ( array_key_exists('MoreCategories', $object->VirtualFields) ) {
+			// set item's additional categories to virtual field (used in editing)
+			$item_categories = $this->getItemCategories($object->GetDBField('ResourceId'));
+			$object->SetDBField('MoreCategories', $item_categories ? '|'.implode('|', $item_categories).'|' : '');
+		}
 	}
 
 	function OnAfterItemUpdate(&$event)