     private function deleteAllPendingResponders():void
     {
         for each (var responder:ListItemResponder in pendingResponders)
-            responder.index = -1;
+        {
+            if (responder)
+                responder.index = -1;
+        }
         pendingResponders.length = 0;
     }
 

    public function getItemIndex(item:Object):int
    {
        for each (var responder:ListItemResponder in pendingResponders)
            if (responder.item === item)
                return responder.index;
        return (list) ? list.getItemIndex(item) : -1;
    }

        {
            var nRequests:int = 0;
            for each (var responder:ListItemResponder in pendingResponders)
            {
                if (responder)
                    nRequests += 1;
            }
            s += " length=" + length + ", " + nRequests + " pending requests";
        }
        else
