         
         private function acceptCompletion() : void {            
             var proposedSelectedItem : Object;            
-            if (_collection.length > 0 && list.selectedIndex >= 0) {
+            if (_collection &&
+                _collection.length > 0 && 
+                list.selectedIndex >= 0) {
                 _completionAccepted = true;
                 proposedSelectedItem = _collection.getItemAt(list.selectedIndex);
             }

        }
        
        private function onMouseWheel(event : MouseEvent) : void {
            
            trace ("event.target=", event.target);
            if (!(DisplayObjectContainer(list).contains(DisplayObject(event.target)) && event.isDefaultPrevented())) {
                hidePopUp();
            }

                case Keyboard.PAGE_DOWN: 
                    list.focusListUponKeyboardNavigation(event);                                     			
                    break;                   
                case Keyboard.ENTER:                    
                    acceptCompletion();
                    
                    break;
                case Keyboard.TAB:
                case Keyboard.ESCAPE:
