Index: includes/menu.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/menu.inc,v
retrieving revision 1.255.2.31
diff -u -p -r1.255.2.31 menu.inc
--- includes/menu.inc	27 Apr 2009 12:50:13 -0000	1.255.2.31
+++ includes/menu.inc	15 Aug 2009 22:28:41 -0000
@@ -1891,7 +1891,7 @@ function menu_link_save(&$item) {
     $existing_item = db_fetch_array(db_query("SELECT * FROM {menu_links} WHERE mlid = %d", $item['mlid']));
   }
 
-  if (isset($item['plid'])) {
+  if (!empty($item['plid'])) {
     $parent = db_fetch_array(db_query("SELECT * FROM {menu_links} WHERE mlid = %d", $item['plid']));
   }
   else {