我正在获取ArgumentError：错误＃2025：

这是我的代码。请任何人可以帮助我。我是一个初学者。
它给了我这个错误

ArgumentError：错误＃2025：提供的DisplayObject必须是调用方的子级。在flash.display :: DisplayObjectContainer / removeChild（）在final2_fla :: MainTimeline / loop（）

import flash.events.Event;
 import flash.events.MouseEvent;
 var kUp:Boolean = false;
var kDn:Boolean = false;
var kLt:Boolean = false;
var kRt:Boolean = false;
var speedX:Number = 0;
var speedY:Number = 0;
var level:Array=new Array();
var scr:Number = 0;
var cn_arr:Array = new Array();
var score:Number = 0;
var rep:Replay=new Replay();
var player:Player=new Player();
addChild(player);
player.x=200;
player.y=250;
//scoreboard.txt.text = score.toString();
var camera = new Rectangle(0,0,stage.stageWidth,stage.stageHeight);
var scoreboard:ScoreBoard = new ScoreBoard();
addChild(scoreboard);
for (var i:int = 0; i< numChildren; i++)
{
    if (getChildAt(i) is platform)
    {
        level.push(getChildAt(i).getRect(this));
        //trace("ok");
    }
}
for (i = 0; i<numChildren; i++)
{
    if (getChildAt(i) is cn )
    {
        cn_arr.push(getChildAt(i));
    }
}


function initGame(e:Event):void
{

stage.addEventListener(KeyboardEvent.KEY_DOWN, keyPressed);
stage.addEventListener(KeyboardEvent.KEY_UP, keyReleased);
stage.addEventListener(Event.ENTER_FRAME, loop);
}

function keyPressed(e:KeyboardEvent):void
{
    //trace("pressed");
    if (e.keyCode == Keyboard.A)
    {
        kRt = true;
        //trace("kRt");
    }
    if (e.keyCode == Keyboard.SPACE)
    {
        kUp = true;
        //trace("Jump");

    }
    if (e.keyCode == Keyboard.D)
    {
        kLt = true;
        //trace("kRt");
    }
    if (e.keyCode == Keyboard.S)
    {
        kDn = true;
        //trace("kRt");
    }
}

function keyReleased(e:KeyboardEvent):void
{
    //trace("notpressed");
    if (e.keyCode == Keyboard.A)
    {
        kRt = false;
        //trace("UnkRt");
    }
    if (e.keyCode == Keyboard.SPACE)
    {
        kUp = false;
        //trace("UnkYUp");
    }
    if (e.keyCode == Keyboard.D)
    {
        kLt = false;
        //trace("UnkLT");
    }
    if (e.keyCode == Keyboard.S)
    {
        kDn = false;
        //trace("UnkDN");
    }
}

stage.addEventListener(Event.ENTER_FRAME,initGame);


function loop(e:Event):void
{
    if (kRt)
    {
        speedX = -5;
    }
    else if (kLt)
    {
        speedX = 5;
    }
    else
    {
        speedX *=  0.5;
    }

    player.x +=  speedX;

    for (i=0; i<level.length; i++)
    {
        if (player.getRect(this).intersects(level[i]))
        {
            if (speedX> 0)
            {
                player.x = level[i].left - player.width / 2;

            }
            if (speedX < 0)
            {
                player.x = level[i].right + player.width / 2;
            }
            speedX = 0;
        }

    }

    var jumpable:Boolean = false;
    speedY +=  1;

    player.y +=  speedY;

    for (i=0; i<level.length; i++)
    {
        if (player.getRect(this).intersects(level[i]))
        {
            if (speedY > 0)
            {
                player.y = level[i].top - player.height / 2;
                speedY = 0;
                jumpable = true;
                //player.gotoAndStop("jump");

            }
            if (speedY < 0)
            {
                player.y = level[i].bottom + player.height / 2;
                speedY *=  -0.5;
            }
        }
    }
    for (var j:int=0; j<cn_arr.length; j++)
    {
        if ((cn_arr[j]).hitTestObject(player))
        {
            removeChild(cn_arr[j]);
            //removeChild(cn_arr[j]);
            score +=  2;
            //var a:String=scr.toString();
            scoreboard.txt.text = score.toString();

            //score.x=50;


        }
    }
    if (kUp && jumpable)
    {
        speedY = -15;
    }


    if(player.hitTestObject(ground))
    {
        removeChild(player);
        addChild(rep);
        rep.x=stage.stageWidth/2;
        rep.y=stage.stageHeight/2;

        rep.btn_re.addEventListener(MouseEvent.CLICK,oncl);

        function oncl(e:MouseEvent):void
        {
            removeChild(rep);
            addChild(player);
            player.x=166;
            player.y=205;
        }
    }
    scoreboard.x = camera.x + 280;
    scoreboard.y = camera.y + 370;
    /*trace(scoreboard.y + " score");
    trace(camera.y);*/

    camera.x = (player.x - camera.width+150);
    camera.y = (player.y - camera.height+250);



    if (camera.x >= 2000)
    {
        camera.x = 2000;
    }

    if (camera.x <= 0)
    {
        camera.x = 0;
    }
    if (camera.y >= 0)
    {
        camera.y = 0;
    }
    if (camera.y <= -610)
    {
        camera.y = -610;
    }
    scrollRect = camera;

}

    enter code here