How to refer to a single frame in a an object class? - actionscript-3

Question

So, I have my character movieclip on frame1 of my timeline. When it hits an enemy the movie goes on frame2 where I have a game-over screen. However I get this error at runtime when the character hits the enemy:
TypeError: Error #2007: Parameter hitTestObject must be non-null.
at flash.display::DisplayObject/_hitTest()
at flash.display::DisplayObject/hitTestObject()
at Coinsy/update()
TypeError: Error #1009: Cannot access a property or method of a null object reference.
at Untitled_2_fla::MainTimeline/CharMovement()
TypeError: Error #1009: Cannot access a property or method of a null object reference.
at Untitled_2_fla::MainTimeline/ResetBox()
TypeError: Error #1009: Cannot access a property or method of a null object reference.
at Untitled_2_fla::MainTimeline/EnemyBall()
I debugged and it seems that the problem is in my coins class:
package
{
import flash.display.*;
import flash.events.*;
public class Coinsy extends MovieClip
{
var char:MovieClip;
var MTL = MovieClip(root);
public function Coinsy()
{
this.addEventListener(Event.ENTER_FRAME, update);
}
function update(event:Event):void
{
char = MTL.char1;
// CC = int(root).CC;
if(hitTestObject(char))
{
this.removeEventListener(Event.ENTER_FRAME, update);
parent.removeChild(this);
MTL.CC++;
}
}
}
}
at char = MTL.char1;, apparently I can't use MovieClip(root) when I have more then one frame.
char1 is my character's instance name andCC is the coin count var.
I'm pretty new at ActionScript and I'd like to know where i did wrong. THANKS!

Answer 1

The error is actually happening on this line
if(hitTestObject(char))
What's happening is the game is still trying to check for collisions on the game-over screen. The char1 object couldn't be found, so it became null. Null essentially means something's empty, so you can't do anything with it. If you ever try null.something you'll get an error, and someFunction(null) will quite likely cause an error too.
A quick fix is changing the line to
if(char != null && hitTestObject(char))
as Karma mentioned.
However, the following three TypeErrors are unrelated to the code you posted. They're happening because some line of code is trying to do null.something. The CharMovement, ResetBox and EnemyBall functions are probably being called when they shouldn't be. You might need to remove event listeners when game-over happens, or add extra logic to check for null values.