Actionscript 3 returns Error #1009 - actionscript-3

Question

I am creating a shooting game. I have encountered a problem with my code when I decided to create a method to remove the missile after reaching the top of the stage. I can run the program without any issues only I have realize that the missile was not remove away from the stage, if I hold the shooting button. However, if I tap the shooting button, the missile will removed away with this error #1009 printing out of the output.
Is there any solution to fix the problem?
Here's is the error after the missile flew to the top of the stage with debugging enabled:
TypeError: Error #1009: Cannot access a property or method of a null object reference.
at Missle/destroyMissle()[E:\Experiment\ExperimentProject\Missle.as:39]
at main/checkMissleOffScreen()[E:\Experiment\ExperimentProject\main.as:63]
at main/eventUpdated()[E:\Experiment\ExperimentProject\main.as:51]
Here's the main's class:
package
{
import flash.display.MovieClip;
import flash.events.Event;
import flash.events.KeyboardEvent;
/**
* ...
* #author test
*/
public class main extends MovieClip
{
//Objects
public var rect:MovieClip;
public var missle:Missle;
//Array
private var missleArray:Array;
//Keyboard section
var leftKeyIsDown:Boolean;
var rightKeyIsDown:Boolean;
var upKeyIsDown:Boolean;
var downKeyIsDown:Boolean;
var spaceKeyIsDown:Boolean;
//Speed
var characterSpeed:Number = 15;
//Main constructor
public function main()
{
//Array initializer
missleArray = new Array();
missle = new Missle();
//Update events listeners.
stage.addEventListener(Event.ENTER_FRAME, eventUpdated);
//Update keyboard events listeners
stage.addEventListener(KeyboardEvent.KEY_DOWN, keyPressed);
stage.addEventListener(KeyboardEvent.KEY_UP, keyUnpressed);
}
//Events functions
//This functions updated everytime the object is move
private function eventUpdated(e:Event):void
{
playerMoving();
playerClampMoving();
checkMissleOffScreen();
}
private function checkMissleOffScreen():void
{
for (var i = 0; i < missleArray.length; i++ )
{
var currentMissle:Missle = missleArray[i];
if (currentMissle.y < 0)
{
missleArray.splice(i, 1);
missle.destroyMissle();
}
}
}
private function playerClampMoving():void
{
if (rect.x < 0)
{
rect.x = 0;
}
if (rect.x > stage.stageWidth - rect.width)
{
rect.x = stage.stageWidth - rect.width;
}
if (rect.y < 0)
{
rect.y = 0;
}
if (rect.y > stage.stageHeight - rect.height)
{
rect.y = stage.stageHeight - rect.height;
}
}
private function playerMoving():void
{
if (leftKeyIsDown == true)
{
rect.x -= characterSpeed;
}
if (rightKeyIsDown == true)
{
rect.x += characterSpeed;
}
if (upKeyIsDown == true)
{
rect.y -= characterSpeed;
}
if (downKeyIsDown == true)
{
rect.y += characterSpeed;
}
if (spaceKeyIsDown == true)
{
shootingMissle();
}
}
private function shootingMissle():void
{
missle = new Missle();
missle.x = rect.x + (rect.width / 2);
missle.y = rect.y;
missleArray.push(missle);
trace(missleArray.length);
stage.addChild(missle);
}
//Keyboard functions
//Check to see whether the user releases the keyboard
private function keyUnpressed(e:KeyboardEvent):void
{
if (e.keyCode == 37)
{
leftKeyIsDown = false;
}
if (e.keyCode == 39)
{
rightKeyIsDown = false;
}
if (e.keyCode == 40)
{
downKeyIsDown = false;
}
if (e.keyCode == 38)
{
upKeyIsDown = false;
}
if (e.keyCode == 32)
{
spaceKeyIsDown = false;
}
}
//Check to see whether the user presses the keyboard
private function keyPressed(e:KeyboardEvent):void
{
if (e.keyCode == 37)
{
leftKeyIsDown = true;
}
if (e.keyCode == 39)
{
rightKeyIsDown = true;
}
if (e.keyCode == 40)
{
downKeyIsDown = true;
}
if (e.keyCode == 38)
{
upKeyIsDown = true;
}
if (e.keyCode == 32)
{
spaceKeyIsDown = true;
}
}
}
}
Here's the Missle's Class:
package
{
import flash.display.Sprite;
import flash.events.Event;
/**
* ...
* #author test
*/
public class Missle extends Sprite
{
public function Missle()
{
addEventListener(Event.ADDED_TO_STAGE, onAdd);
}
private function onAdd(e:Event):void
{
removeEventListener(Event.ADDED_TO_STAGE, onAdd);
//Objects are on the stage
init();
}
private function init():void
{
addEventListener(Event.ENTER_FRAME, missleLaunch);
}
private function missleLaunch(e:Event):void
{
this.y -= 15;
}
public function destroyMissle():void
{
parent.removeChild(this);
removeEventListener(Event.ENTER_FRAME, missleLaunch);
}
}
}

Answer 1

Try this:
public function destroyMissle():void
{
if(parent !== null) parent.removeChild(this);
removeEventListener(Event.ENTER_FRAME, missleLaunch);
}
It is a possibility that you were calling .destroyMissile() more than once meaning parent would be null because you've removed it from the stage and it has no parent.