Index: core/kernel/db/db_event_handler.php
===================================================================
--- core/kernel/db/db_event_handler.php	(revision 13350)
+++ core/kernel/db/db_event_handler.php	(working copy)
@@ -852,8 +852,8 @@
 
 			$sorting_configs = $this->Application->getUnitOption($event->Prefix, 'ConfigMapping');
 			$list_sortings = $this->Application->getUnitOption($event->Prefix, 'ListSortings');
-			$sorting_prefix = getArrayValue($list_sortings, $event->Special) ? $event->Special : '';
-
+			$sorting_prefix = array_key_exists($event->Special, $list_sortings) ? $event->Special : '';
+							
 			$tag_sort_by = $event->getEventParam('sort_by');
 			if ($tag_sort_by) {
 				if ($tag_sort_by == 'random') {