Null object reference

1

this code is working:

for(i = 0; i < 8; i++){
 graphicDesignArray*.addEventListener(MouseEvent.ROLL_OVER,buildOverGDThumb(i));
            }

    function buildOverGDThumb(number:Number): Function {
        var thisVar: Object = this;
        var over: Function = function(event:MouseEvent){
        var target = event.target;
        thisVar.setChildIndex(target,thisVar.numChildren - 1);
        TweenMax.to(graphicDesignArray[number],.5,{scale:thumbScaleOver,x:thumbPosXArray[number],y:thumbPosYArray[number],ease:Back.easeOut});
            
        }
        return over;
    }

I’m getting the error:Cannot access a property or method of a null object reference with this:

for(var i = 0; i < 8; i++){       graphicDesignArray*.addEventListener(MouseEvent.CLICK,buildOnGDThumb(i));
            }

function buildOnGDThumb(number:Number): Function {
    
        var onFunction: Function = function(event:MouseEvent){
                if(imageState == "off"){
               
            thumbTimelineArray[number] = new TimelineLite();
            thumbTimelineArray[number].insertMultiple([
            TweenMax.to(graphicDesignArray[number],.5,{scale:1,x:450,y:350,ease:Back.easeOut}),
            TweenMax.to(whiteBg,.5,{scale:1,x:0,y:0,ease:Back.easeOut}),
            ], 0, TweenAlign.START, 0.3);
                imageState = "on"
                }else{
            TweenMax.to(graphicDesignArray[number],.5,{scale:thumbScaleOver,x:thumbPosXArray[number],y:thumbPosYArray[number],ease:Back.easeOut});
                
                imageState = "off"
                }
        }
        return onFunction;
    }

I don’t know why.