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

        const r:Array = new Array();
        var index:int = 0;
        for each (var item:* in a)
            r[index++] = item;
        return r;
    }
    

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