В конце проигрывания ролика с этим слайдером все картинки появляются на экране вопреки маске

Код AS3:
import com.greensock.*;
import com.greensock.easing.*;
var xml:XML;
var images:Array = new Array();
var totalImages:Number;
var nbDisplayed:Number = 1;
var imagesLoaded:int = 0;
var slideTo:Number = 0;
var imageWidth = 600;
var container_mc:MovieClip = new MovieClip();
slider_mc.addChild(container_mc);
container_mc.mask = slider_mc.mask_mc;
function loadXML(file:String):void{
var xmlLoader:URLLoader = new URLLoader();
xmlLoader.load(new URLRequest(file));
xmlLoader.addEventListener(Event.COMPLETE, parseXML);
}
function parseXML(e:Event):void{
xml = new XML(e.target.data);
totalImages = xml.children().length();
loadImages();
}
function loadImages():void{
for(var i:int = 0; i<totalImages; i++){
var loader:Loader = new Loader();
loader.load(new URLRequest("images/"+String(xml.children()[i].@src)));
images.push(loader);
loader.contentLoaderInfo.addEventListener(ProgressEvent.PROGRESS,onProgress);
loader.contentLoaderInfo.addEventListener(Event.COMPLETE,onComplete);
}
}
function onProgress(e:ProgressEvent):void{
loading_txt.text = "Loading " + imagesLoaded + " / " + totalImages;
}
function onComplete(e:Event):void{
imagesLoaded++;
if(imagesLoaded == totalImages){
loading_txt.text = "";
createImages();
}
}
function createImages():void{
for(var i:int = 0; i < images.length; i++){
var bm:Bitmap = new Bitmap();
bm = Bitmap(images[i].content);
bm.smoothing = true;
bm.x = i*imageWidth;
container_mc.addChild(bm);
}
}
previous_btn.addEventListener(MouseEvent.CLICK,slideLeft);
next_btn.addEventListener(MouseEvent.CLICK,slideRight);
function slideLeft(e:MouseEvent):void{
slideTo -= nbDisplayed;
slideContainer();
}
function slideRight(e:Event):void{
slideTo += nbDisplayed;
slideContainer();
}
function slideContainer():void{
if(totalImages - slideTo < nbDisplayed)
slideTo = totalImages - nbDisplayed;
if(slideTo < 0)
slideTo = 0;
TweenLite.to(container_mc,.5,{x: -slideTo*imageWidth,ease:Quad.easeIn});
}
stage.addEventListener(KeyboardEvent.KEY_DOWN,keyHandler);
function keyHandler(evt:KeyboardEvent) {
if(evt.keyCode == Keyboard.LEFT) slideLeft(null);
else if(evt.keyCode == Keyboard.RIGHT) slideRight(null);
}
loadXML("datas.xml");