Projectiles not moving as they are supposed to - actionscript-3

Question

package
{
import flash.display.MovieClip;
import flash.events.Event;
import flash.ui.Keyboard;
import flash.events.KeyboardEvent;
import flash.events.MouseEvent;
public class supportForce extends MovieClip
{
public function supportForce()
{
stage.addEventListener(KeyboardEvent.KEY_DOWN, onDown);
stage.addEventListener(KeyboardEvent.KEY_UP, onUp);
stage.addEventListener(Event.ENTER_FRAME, keyCheck);
}
private function onUp(e:KeyboardEvent):void
{
_keyDownStatus[e.keyCode] = false;
}
private function onDown(e:KeyboardEvent):void
{
_keyDownStatus[e.keyCode] = true;
}
private function keyCheck(event:Event)
{
if (_keyDownStatus[90])
{
var GreenLight:Projectile1 = new Projectile1();
stage.addChild(GreenLight);
GreenLight.x = Player2Child.x;
GreenLight.y = Player2Child.y;
}
GreenLight.x -= defaultSpeed;
}
}
}
So the projectile here is Projectile1 and it is declared as GreenLight in the keyCheck Function. So in the same function (the ENTER.FRAME function) GreenLight is supposed to move to its left. This does not happen and also an error saying TypeError: Error #1009: Cannot access a property or method of a null object reference.
at supportForce/keyCheck() appears. Thank you in advance.

Answer 1

In your keyCheck function, GreenLight will be null if _keyDownStatus[90] is false
so put the GreenLight as a class variable
private var lights:Array = [];
private function keyCheck(event:Event)
{
if (_keyDownStatus[90])
{
var GreenLight:Projectile1 = new Projectile1();
stage.addChild(GreenLight);
GreenLight.x = Player2Child.x;
GreenLight.y = Player2Child.y;
for each (var l:Projectile1 in lights)
{
l.x -= defaultSpeed;
}
lights.push(GreenLight);
}
else
{
//remove all Projectile1s in lights from stage and clear lights if you want
}
}

Answer 2

you create GreenLight in if condition scope and if keyCode isnot 90, object of Projectile1 isnot created and GreenLight.x -= defaultSpeed; there GreenLight is null