Index: branches/RC/core/units/categories/categories_event_handler.php
===================================================================
diff -u -r10671 -r10780
--- branches/RC/core/units/categories/categories_event_handler.php	(.../categories_event_handler.php)	(revision 10671)
+++ branches/RC/core/units/categories/categories_event_handler.php	(.../categories_event_handler.php)	(revision 10780)
@@ -224,8 +224,12 @@
 			}
 
 			$rel_table = $this->Application->getUnitOption('rel', 'TableName');
-			$item_type = $this->Application->getUnitOption($event->Prefix, 'ItemType');
+			$item_type = (int)$this->Application->getUnitOption($event->Prefix, 'ItemType');
 
+			if ($item_type == 0) {
+				trigger_error('<strong>ItemType</strong> not defined for prefix <strong>' . $event->Prefix . '</strong>', E_USER_WARNING);
+			}
+
 			// process case, then this list is called inside another list
 			$prefix_special = $event->getEventParam('PrefixSpecial');
 			if (!$prefix_special) {