PreLoader

[tbhD41]

Hey

I have made an applikation there are build up in classes.

Now i have build a preloader to load my application but i get this error: TypeError: Error #1009: Cannot access a property or method of a null object reference.
at Main() <— my Main class in the application not the preloader Main:be:

My preLoader Main class:

package {
    import flash.display.Loader;
    import flash.display.Sprite;
    import flash.events.*;
    import flash.net.URLRequest;

    public class LoaderX extends Sprite {
        private var url:String = "App.swf";

        public function LoaderX() {
            var loader:Loader = new Loader();
            configureListeners(loader.contentLoaderInfo);
            loader.addEventListener(MouseEvent.CLICK, clickHandler);

            var request:URLRequest = new URLRequest(url);
            loader.load(request);

            addChild(loader);
        }

        private function configureListeners(dispatcher:IEventDispatcher):void {
            dispatcher.addEventListener(Event.COMPLETE, completeHandler);
            dispatcher.addEventListener(ProgressEvent.PROGRESS, progressHandler);
        }

        private function completeHandler(event:Event):void {
            trace("completeHandler: " + event);
        }

        private function progressHandler(event:ProgressEvent):void {
           // trace("progressHandler: bytesLoaded=" + event.bytesLoaded + " bytesTotal=" + event.bytesTotal);
            var loaded:Number = event.bytesLoaded/event.bytesTotal;
            loaded = Math.round(loaded * 100);
            var string:String= String(loaded);
            pro.text = string;
            trace(string);
            //trace(loaded);
            //tekst.text = numb as String;
        }

        private function clickHandler(event:MouseEvent):void {
           // trace("clickHandler: " + event);
            var loader:Loader = Loader(event.target);
            loader.unload();
        }
    }
}

Are there some who have a better solution?