Error #1069?

I recently opened my Flash Project and i got this error:

ReferenceError: Error #1069: Property borders not found on classes.World and there is no default value.

    at classes::Player()

    at SimplyHuman_fla::MainTimeline/setUp()

    at SimplyHuman_fla::MainTimeline/frame5()

    at flash.display::MovieClip/gotoAndStop()

    at SimplyHuman_fla::MainTimeline/newGame()

Which has never happened before and i've not altered any of the code.

The Player Classes part in Debug it is singling out is this:

public function Player(X:int,Y:int):void
        {
            // keep centered
            this.x = X;
            this.y = Y;
            // add player to collision list with the borders
            myCollisionList = new CollisionList(world.borders);
            myCollisionList.addItem(this);
            // set the shot cool down;
            shotCooldown = MAX_COOLDOWN;
            // check when player is added to stage
            addEventListener(Event.ADDED_TO_STAGE,init);
            addEventListener(Event.ENTER_FRAME,updates);
        }

And, Its also referencing to this aswell in the main timeline

world = new classes.World();
inv = new classes.Inventory();
player = new classes.Player(400,240);
stage.addChildAt(world,0);
stage.addChildAt(player,1);
stage.addChildAt(Health,2);

I don't know what to do, Please can someone help me?