Accessing raw sound data tutorial...

Hi,

?Just tried importing the Accessing raw sound data (http://livedocs.adobe.com/flex/3/html/help.html?content=Working_with_Sound_14.ht ml) tutorial into flex builder.?It now compiles now, altrhough I needed to include ByteArray import, but when I run it the debug window displays:

Cannot access a property or method of a null object reference.

If I hit continue the music plays though.?I have included the code below:

package {
?import flash.display.Sprite;

?public class waveform_example_as extends Sprite
?{
?public function waveform_example_as()
?{?
?import flash.utils.ByteArray;
?import flash.display.Graphics;
?import flash.events.Event;
?import flash.media.Sound;
?import flash.media.SoundChannel;
?import flash.media.SoundMixer;
?import flash.net.URLRequest;
?
?const PLOT_HEIGHT:int = 200;
?const CHANNEL_LENGTH:int = 256;
?
?var snd:Sound = new Sound();
?var req:URLRequest = new URLRequest(''tester.mp3'');
?snd.load(req);

?var channel:SoundChannel;
?channel = snd.play();
?addEventListener(Event.ENTER_FRAME, onEnterFrame);
?snd.addEventListener(Event.SOUND_COMPLETE, onPlaybackComplete);
?
?var bytes:ByteArray = new ByteArray();
?
?function onEnterFrame(event:Event):void
?{
?SoundMixer.computeSpectrum(bytes, false, 0);
?
?var g:Graphics = this.graphics;
?
?g.clear();
?g.lineStyle(0, 0x6600CC);
?g.beginFill(0x6600CC);
?g.moveTo(0, PLOT_HEIGHT);
?
?var n:Number = 0;
?
?// left channel
?for (var i:int = 0; i %26lt; CHANNEL_LENGTH; i++)
?{
?n = (bytes.readFloat() * PLOT_HEIGHT);
?g.lineTo(i * 2, PLOT_HEIGHT - n);
?}
?g.lineTo(CHANNEL_LENGTH * 2, PLOT_HEIGHT);
?g.endFill();
?
?// right channel
?g.lineStyle(0, 0xCC0066);
?g.beginFill(0xCC0066, 0.5);
?g.moveTo(CHANNEL_LENGTH * 2, PLOT_HEIGHT);
?
?for (i = CHANNEL_LENGTH; i %26gt; 0; i--)
?{
?n = (bytes.readFloat() * PLOT_HEIGHT);
?g.lineTo(i * 2, PLOT_HEIGHT - n);
?}
?g.lineTo(0, PLOT_HEIGHT);
?g.endFill();
?}
?
?function onPlaybackComplete(event:Event):void
?{
?removeEventListener(Event.ENTER_FRAME, onEnterFrame);
?}
?
?}
?}
}

Thanks,

Paul.