AS3 Going backwards in an Array of MovieClips for an image gallery

programming flash
1

I am trying to make a back button work for an image gallery with MovieClips in an array. I want to go backwards in the image gallery and am coming up with this error:

TypeError: Error #2007: Parameter child must be non-null.
at flash.display::DisplayObjectContainer/removeChild()
at DigitalSignage_Gallery_fla::MainTimeline/lastPick()

Here is the code:

var Fullsize_Pic:Array = new Array();

Fullsize_Pic[0] = new Fullsize_01();
Fullsize_Pic[1] = new Fullsize_02();
Fullsize_Pic[2] = new Fullsize_03();

//Defines first image
var aPic = 0;

addChild(Fullsize_Pic[aPic]);

//Event Listeners for buttons
Controls.Button1.addEventListener(MouseEvent.CLICK, lastPick);
//Controls.Button2.addEventListener(MouseEvent.CLICK, nextPick);

//Changing fullsize images
function lastPick(event:MouseEvent):void
{
if (aPic == 0)
{
var bPic = 34;

removeChild(Fullsize_Pic[aPic]);
addChild(Fullsize_Pic[bPic]);

var aPic = bPic;
}
else {

var bPic = aPic - 1;

removeChild(Fullsize_Pic[aPic]);
addChild(Fullsize_Pic[bPic]);

var aPic = bPic;
}

}

Cheers! And thanks for the help in advance :slight_smile: