Problem with volume handle and external SWF

Question

Hello I'm having 2 problems.
The first is that when loading an external swf in my main SWF I get this in the output window:
TypeError: Error #1009: Cannot access a property or method of a null object reference.
at audio_fla::list_1/frame1()
at flash.display::Sprite/constructChildren()
at flash.display::Sprite()
at flash.display::MovieClip()
at audio_fla::MainTimeline()
TypeError: Error #1009: Cannot access a property or method of a null object reference.
at audio_fla::MainTimeline/frame1()
But it still works. Its an mp3 player.
The other problem is that the loaded SWF has a volume controller. When I test the external SWF by itself it works fine. When I load it on my main SWF when I start to drag the handle on my volume slider and MOUSE_UP outside the handle it still keep dragging the handle.
The code of my main SWF is:
import caurina.transitions.*;
var _currentCategory:String = "";
var percent:String = "";
var loader = new Loader();
loader.name="videoLoader";
loadermc.visible=false;
cat.addEventListener(MouseEvent.MOUSE_OVER, onOverCat);
cat.addEventListener(MouseEvent.MOUSE_OUT, onOutCat);
cat.addEventListener(MouseEvent.CLICK, onClickCat);
btnback.addEventListener(MouseEvent.MOUSE_OVER, onOverCat);
btnback.addEventListener(MouseEvent.MOUSE_OUT, onOutCat);
btnback.addEventListener(MouseEvent.CLICK, onClickBack);
cat.buttonMode = true;
btnback.buttonMode = false;
btnback.visible = false;
function onOverCat(e:MouseEvent):void{
     Tweener.addTween(e.target, {alpha:.5 , time:.5});
function onOutCat(e:MouseEvent):void{
     Tweener.addTween(e.target, {alpha:.25 , time:.5});
function onClickBack(e:MouseEvent):void{
     loader.unloadAndStop();
     loader.contentLoaderInfo.addEventListener(IOErrorEvent.IO_ERROR, ioErrorHandler);
     lcontent.visible = false;
     cat.visible = true;
     Tweener.addTween(cat, {alpha:1, time:1});
     btnback.buttonMode = false;
     btnback.visible = false;
     cat.buttonMode = true;
     toptxt.text = "SELECCIONE UNA CATEGORIA"
function onClickCat(e:MouseEvent):void{
     lcontent.visible=true;
     cat.buttonMode = false;
     Tweener.addTween(cat, {alpha:0, time:1, onComplete:function(){
                              cat.visible = false;                                                       
                              btnback.buttonMode = true;
                              btnback.visible = true;
                                   loaderTweenIn(e.target.name);
function loaderTweenIn (c:String):void{
     var category:String = c+".swf";
     trace(category);
     loader.load(new URLRequest(category));
     loader.contentLoaderInfo.addEventListener (Event.COMPLETE, movieLoaded);
        loader.contentLoaderInfo.addEventListener(ProgressEvent.PROGRESS, movieProgress);
function ioErrorHandler(e:IOErrorEvent):void{
     trace("ioErrorHanlder: "+e);
function movieLoaded(e:Event):void{
     trace("The movie has loaded");
     lcontent.addChild(loader);
     loadermc.visible=false;
function movieProgress(e:ProgressEvent):void{
     loadermc.visible = true;
//     percent=String(Math.floor(e.bytesLoaded / e.bytesTotal * 100)) + "%";
     trace("The movie is loading "+Math.floor(e.bytesLoaded / e.bytesTotal * 100));
The code on my external SWF is:
import caurina.transitions.*;
volume_mc.slider_mc.buttonMode = true;
var myXML:XML;
var thb:Thbs;
var myThumbs:XMLList;
var totalThumbs:Number;
var thumbHeight:Number=50;
var i:uint = 0;
var preloader:LoaderAnim;
var yCounter:Number = 0;
var container:MovieClip;
var musicReq:URLRequest;
var music:Sound = new Sound();
var sc:SoundChannel;
var currentSound:Sound = music;
var pos:Number;
var songPlaying:Boolean = false;
var songlist:XMLList;
var currentIndex:Number = 0;
mc_sound.mute.visible=false;
var xmlLoader:URLLoader = new URLLoader();
///////////////////////////PLAYLIST//////////////////
function initMediaPlayer(e:Event):void{
     myXML = new XML(xmlLoader.data);     
     myThumbs = myXML.*;
     totalThumbs = myThumbs.length();
     trace("The total thumbs are "+totalThumbs);
     createContainer();
     callThumbs();
xmlLoader.load(new URLRequest("audio.xml"));
function createContainer():void{
     container = new MovieClip();
     list.ch.addChild(container);
     container.y = 0;
     container.x = 0;
     container.buttonMode = true;
function onOver(e:MouseEvent):void{
     var t:Loader = Loader(e.target);
     Tweener.addTween(t, {alpha:.5, time:1});
function onOut(e:MouseEvent):void{     
     var t:Loader = Loader(e.target);
     Tweener.addTween(t, {alpha:1, time:1});
function callThumbs():void{
          var thumbURL = myThumbs[i].@thumb;
          var thumbTitle:String = myThumbs[i].@title;
          var thumbDesc:String = myThumbs[i];
          trace("Loading "+thumbURL);
          trace("Title "+thumbTitle);
          trace("Desc "+thumbDesc);
          var thumbLoader = new Loader();
          thumbLoader.load(new URLRequest(thumbURL));
          thumbLoader.contentLoaderInfo.addEventListener(Event.COMPLETE, thumbLoaded);
          thumbLoader.name=i;
          thumbLoader.x=5;
          thumbLoader.y=5;
          thb = new Thbs();
          container.addChild(thb);
          thb.thb_title.htmlText = thumbTitle;
          thb.thb_desc.autoSize = TextFieldAutoSize.LEFT;
          thb.thb_desc.htmlText = thumbDesc;
          thb.y = (thumbHeight+2)*yCounter;
          preloader = new LoaderAnim();
          preloader.x = thb.x + 20;
          preloader.y = thb.y+ 20;
          container.addChild(preloader);
          yCounter++;
function thumbLoaded(e:Event):void{
     var thbx:Loader = Loader(e.target.loader);
     thb.addChild(thbx);
     thbx.addEventListener(MouseEvent.MOUSE_OVER, onOver);
     thbx.addEventListener(MouseEvent.MOUSE_OUT, onOut);
     container.removeChild(preloader);
     i++;
     if (i<totalThumbs){
          callThumbs();
     if (i==totalThumbs){
          startAudio();
xmlLoader.addEventListener(Event.COMPLETE, initMediaPlayer);
///////////////////////////////////////AUDIO//////////////////////////
function startAudio():void{
     songlist = myXML.*;;//this is the same as myXML.*;
     trace("This is the first song "+songlist[0].@song);
     musicReq = new URLRequest(songlist[0].@song);
     music.load(musicReq);
     sc = music.play();
     sc.addEventListener(Event.SOUND_COMPLETE, nextSong);     
next_btn.addEventListener(MouseEvent.CLICK, nextSong);
prev_btn.addEventListener(MouseEvent.CLICK, prevSong);
pause_btn.addEventListener(MouseEvent.CLICK,pauseSong);
stop_btn.addEventListener(MouseEvent.CLICK,stopSong);
function nextSong(e:Event):void
     if (currentIndex < (songlist.length() - 1))
          currentIndex++;
     else
          currentIndex = 0;
     var nextReq:URLRequest = new URLRequest(songlist[currentIndex].@song);
     var nextTitle:Sound = new Sound(nextReq);
     sc.stop();
     sc = nextTitle.play();
     songPlaying = true;
     currentSound = nextTitle;
     sc.addEventListener(Event.SOUND_COMPLETE, nextSong);
function prevSong(e:Event):void
     if (currentIndex > 0)
          currentIndex--;
     else
          currentIndex = songlist.length() - 1;
     var nextReq:URLRequest = new URLRequest(songlist[currentIndex].@song);
     var prevTitle:Sound = new Sound(nextReq);
     sc.stop();
     sc = prevTitle.play();
     songPlaying = true;
     currentSound = prevTitle;
     sc.addEventListener(Event.SOUND_COMPLETE, nextSong);
function pauseSong(e:Event):void
     pos = sc.position;
     sc.stop();
     songPlaying = false;
     play_btn.addEventListener(MouseEvent.CLICK,playSong);
function playSong(e:Event):void
     if(songPlaying == false)
          sc = currentSound.play(pos);
          sc.addEventListener(Event.SOUND_COMPLETE, nextSong);
          songPlaying = true;
          play_btn.removeEventListener(MouseEvent.CLICK,playSong);
function stopSong(e:Event):void
     sc.stop();
     pos = 0;
     songPlaying = false;
     play_btn.addEventListener(MouseEvent.CLICK,playSong);
///////////////////////////////VOLUME/////////////////////////////
var xOffset:Number;
var xMin:Number = 0;
var xMax:Number = volume_mc.track.width;
volume_mc.slider_mc.addEventListener(MouseEvent.MOUSE_DOWN, sliderDown);
volume_mc.slider_mc.addEventListener(MouseEvent.MOUSE_UP, sliderUp);
stage.addEventListener(MouseEvent.MOUSE_UP, sliderUp);
function sliderDown(e:MouseEvent):void{
     stage.addEventListener(MouseEvent.MOUSE_MOVE, sliderMove);
     xOffset = mouseX - volume_mc.slider_mc.x;
function sliderUp(e:MouseEvent):void{
     stage.removeEventListener(MouseEvent.MOUSE_MOVE, sliderMove);
function sliderMove(e:MouseEvent):void{
     volume_mc.slider_mc.x = mouseX - xOffset;
     if(volume_mc.slider_mc.x<=xMin){
          volume_mc.slider_mc.x = xMin;
     if(volume_mc.slider_mc.x>=xMax){
          volume_mc.slider_mc.x = xMax;
     var vol:Number = volume_mc.slider_mc.x*.01;
     var st:SoundTransform = new SoundTransform(vol,0);
     sc.soundTransform = st;
     trace("The volume is "+vol);
     if(vol==0){
          mc_sound.mute.visible=true;
     }else{
          mc_sound.mute.visible=false;
     e.updateAfterEvent();

Answer 1

I found the solution.