Error #1009: Cannot access a property or method of a null object reference.on camera

Question

im working on augmented reality application where my augmented object can be touched by hands. So it has motion detection in it. i build it using flartoolkit and away3d.

I already made the augmented reality and motion detection part. The problem is where i combined them,

I get the class for motion detection from http://blog.soulwire.co.uk/code/actionscript-3/webcam-motion-detection-tracking

Whenever i try to run my program, it get Error #1009: Cannot access a property or method of a null object reference.on camera

from what i analyze, my code cant differentiate which camera that i use. If anyone can show hot to fix it, it will help me a lot

here's initialization for camera in augmented reality part

this.flarManager.removeEventListener(Event.INIT, this.onFlarManagerInited);

        this.camera3D = new FLARCamera_Away3D(this.flarManager, new Rectangle(0, 0, this.stage.stageWidth, this.stage.stageHeight));
        this.view = new View3D({x:0.5*this.stage.stageWidth, y:0.5*this.stage.stageHeight, scene:this.scene3D, camera:this.camera3D});
        this.addChild(this.view);

        this.light = new DirectionalLight3D();
        this.light.direction = new Vector3D(500, -300, 200);
        this.scene3D.addLight(light);

and here's initialization for camera in my motion detection part

        var camW : int = 420;
        var camH : int = 320;

        // Create the camera
        var cam : Camera = Camera.getCamera();
        cam.setMode(camW, camH, stage.frameRate);

        // Create a video
        var vid : Video = new Video(camW, camH);
        vid.attachCamera(cam);