Flash XML Galerija

Pozdravljeni!
Tole napako mi javi, ko hočem prikazati foto galerijo, pa ne najdem rešitve. Mi lahko kdo prosim pomaga?

TypeError: Error #1009: Cannot access a property or method of a null object reference.
at Main()
TypeError: Error #1009: Cannot access a property or method of a null object reference.
at Main/parseXML()
at flash.events::EventDispatcher/dispatchEventFunction()
at flash.events::EventDispatcher/dispatchEvent()
at flash.net::URLLoader/onComplete()


pa še main datoteka

package {
import flash.display.*;
import flash.events.*;
import flash.text.*;
import flash.net.*;

public class Main extends MovieClip {
public var currentImg:Number;
public var lastImg:Number;
public var xml:XML;
public var loader:Loader;
public var xmlLoader:URLLoader;

public function Main() {
loader = new Loader();
addChild(loader);

xmlLoader = new URLLoader(new URLRequest("/gallery.xml"));
xmlLoader.addEventListener(Event.COMPLETE, parseXML);

left_mc.stop();
right_mc.stop();
}

protected function parseXML(event:Event):void {
left_mc.addEventListener(MouseEvent.MOUSE_UP, nextImg);
left_mc.addEventListener(MouseEvent.MOUSE_OUT, arrowOut);
left_mc.addEventListener(MouseEvent.MOUSE_OVER, arrowOver);
right_mc.addEventListener(MouseEvent.MOUSE_UP, prevImg);
right_mc.addEventListener(MouseEvent.MOUSE_OUT, arrowOut);
right_mc.addEventListener(MouseEvent.MOUSE_OVER, arrowOver);

xml = new XML(event.currentTarget.data);
lastImg = xml.img.length() - 1;
currentImg = 0;
loadImg();
}

protected function loadImg():void {
loader.x = (stage.width - Number(xml.img[currentImg].@width))/2;
loader.y = (stage.height - 50 - Number(xml.img[currentImg].@height))/2;
loader.load(new URLRequest(xml.@dir + xml.img[currentImg].@file));
loader.contentLoaderInfo.addEventListener(Event.COMPLETE, loadFin);
}

protected function loadFin(event:Event):void {
textDisp_TF.htmlText = xml.img[currentImg];
}

protected function arrowOut(event:MouseEvent):void {
MovieClip(event.currentTarget).gotoAndStop(1);
}

protected function arrowOver(event:MouseEvent):void {
MovieClip(event.currentTarget).gotoAndStop(2);
}

protected function nextImg(event:MouseEvent):void {
loader.unload();
currentImg = (currentImg < lastImg)? currentImg + 1 : 0;
loadImg();
}

protected function prevImg(event:MouseEvent):void {
loader.unload();
currentImg = (currentImg > 0)? currentImg - 1 : lastImg;
loadImg();
}
}
}

nisem še ugotovil za ta primer. Sem pa rešil z galerijo na drug način