Level progression in a platform game? (Actionscript 3) - actionscript-3

Question

I've been working on a Platformer for a couple of weeks now and i can't seem to get the level progression working. I'm using a basic hitTest on a box to signal the movement from frame 1(level 1) to frame 2 (level 2) but once the character hits the exit box, i get the following error
TypeError: Error #1009: Cannot access a property or method of a null object reference.
at LevelProg_fla::MainTimeline/loop()
What can i do so that it moves to the next frame(level)? If it helps, my code is in a frame rather than a class. Basically, the only code that i'm using for level progression is
if (player.hitTestObject(exit))
{
gotoAndPlay("levelTwo");
}
with "levelTwo" being the name of the next frame (next level). The rest of the game's code is as follows (pardon the messyness of it, I've been more focused on getting the darn thing to work :b)
import flash.events.KeyboardEvent;
import flash.events.Event;
//some variables to track the player's speed
var speedX = 0;
var speedY = 0;
player.height = 80.0;
player.width = 60.0;
//loop through all the platform objects to generate the level
var level:Array = new Array();
for (var i=0; i<numChildren; i++)
{
if (getChildAt(i) is platform)
{
level.push(getChildAt(i).getRect(this));
}
}
//make variables to store key states
var kUp = false;
var kDown = false;
var kLeft = false;
var kRight = false;
//listen for key presses and releases
stage.addEventListener(KeyboardEvent.KEY_DOWN, kD);
stage.addEventListener(KeyboardEvent.KEY_UP, kU);
function kD(k:KeyboardEvent)
{
if (k.keyCode==37) kLeft=true;
if (k.keyCode==38) kUp=true;
if (k.keyCode==39) kRight=true;
if (k.keyCode==40) kDown=true;
}
function kU(k:KeyboardEvent)
{
if (k.keyCode==37) kLeft=false;
if (k.keyCode==38) kUp=false;
if (k.keyCode==39) kRight=false;
if (k.keyCode==40) kDown=false;
}
//Make a looping function
addEventListener(Event.ENTER_FRAME, loop);
function loop(e:Event)
{
//lateral movement checks
if (kLeft)
{
speedX=-10;
}
else if (kRight)
{
speedX=10;
}
else
{
speedX*=0.5; //friction to slow player down (kinda like mario)
}
//does not stop the character
//move player based on the above
player.x+=speedX;
//animations
if (speedX > 0)
{
trace("right pressed");
//player.gotoAndPlay("walkRight");
}
if (speedX < 0)
{
trace("left pressed");
//player.gotoAndPlay("walkLeft");
}
//sidewards hit tests
for (i=0; i<level.length; i++)
{
if (player.getRect(this).intersects(level[i]))
{
if (speedX > 0) ////moving right collision and stuffs
{
player.x = level[i].left-player.width/2;
}
if (speedX < 0) ////moving left collision and stuffs
{
player.x = level[i].right+player.width/2;
}
//RIGHTIO
speedX = 0 //kills the speed
}
}
//vertical checks
speedY+=1;
player.y+=speedY;
var jumpable = false
//vertical hitTests
//note that it's the same as the x code but just changed like 5 things.
for (i=0; i<level.length; i++)
{
if (player.getRect(this).intersects(level[i]))
{
if (speedY > 0) ////moving down collision and stuffs
{
player.y = level[i].top-player.height/2;
speedY=0;
jumpable = true;
}
if (speedY < 0) ////moving up collision and stuffs
{
player.y = level[i].bottom+player.height/2;
speedY*=-0.5; //bounces off cielings
}
//RIGHTIO
speedX = 0 //kills the speed
}
}
//jumps if possible
if (kUp && jumpable)
{
speedY=-15;
}
//gravity might help}
//move player with camera function/code/script/tired
this.x=-player.x+(stage.stageWidth/2); //centers the player
this.y=-player.y+(stage.stageWidth/2); //centers the player
//Progresses the player to level 2
if (player.hitTestObject(exit))
{
gotoAndPlay("levelTwo");
}
}