TypeError: Error #1009

programming flash
1

All I have on my stage is one MovieClip, instance-named “box_mc”.

On Frame 1 (which is the only frame out there), I have this code:

[AS]
import com.placement.LiquidLayout;

var newAligner:LiquidLayout = new LiquidLayout(box_mc, 300, 300);
addChild(newAligner);[/AS]

And in my class file (which is based on the StageManager class by noponies.com) I have this code:

[AS]
package com.placement {

import flash.display.*;
import flash.display.StageAlign;
import flash.display.StageScaleMode;
import flash.events.Event;

public class LiquidLayout extends Sprite {
    
    //declaring the variables
    private var managedObject:InteractiveObject;
    private var xAxis:Number;
    private var yAxis:Number;
    
    //building the constructor
    public function LiquidLayout(target:InteractiveObject, xpos:Number, ypos:Number) {
        
        //getting local variables
        managedObject = target;
        xAxis = xpos;
        yAxis = ypos;
        
        //executing the actions
        setLayout();
        stage.addEventListener(Event.RESIZE, resizeListener);
        
    }
    
    private function resizeListener() {
        setLayout();            
    }
    
    private function setLayout() {
        managedObject.x = xAxis;
        managedObject.y = yAxis;
    }
    
}

}[/AS]

And when I test my movie, everything works correctly, though I get this in the Output window:

TypeError: Error #1009: Cannot access a property or method of a null object reference.
    at com.placement::LiquidLayout$iinit()
    at test_fla::MainTimeline/test_fla::frame1()

Can anyone explain, why this happens, and how I should fix the class file to have no such warnings in the future.

Thanks in advance, Here are the source files: