HaxeFlixel crashing after FlxG.switchState

GameChangerMain.hx

package;

import nme.Lib;
import org.flixel.FlxGame;
import org.flixel.FlxG;
import org.flixel.FlxSprite;
import org.flixel.FlxState;
    
class GameChangerMain extends FlxGame
{  
	public function new()
	{	
		FlxG.debug = true;

		var stageWidth:Int = Lib.current.stage.stageWidth;
		var stageHeight:Int = Lib.current.stage.stageHeight;
		var ratioX:Float = stageWidth / 320;
		var ratioY:Float = stageHeight / 480;
		var ratio:Float = Math.min(ratioX, ratioY);
		
        super( 80, 120, MenuState, 4, 30, 30);
	}
}

class MenuState extends FlxState
{
	public static var playState:PlayState;
    public static var ball:Agent;

    
	override public function update():Void
	{
        // PRESS SPACE TO CRASH!
		if ( FlxG.keys.justPressed( "SPACE" ) )
		{
        		playState = new PlayState();		
                ball = new Agent();
                playState.add( ball );
                FlxG.switchState( playState );
		}
		super.update();
	}	
}

class Agent extends FlxSprite
{ }

class PlayState extends FlxState
{ }

Main.hx

package;

import nme.display.StageAlign;
import nme.display.StageScaleMode;
import nme.display.Sprite;
import nme.events.Event;
import nme.events.KeyboardEvent;
import nme.Lib;
import nme.ui.Keyboard;
import org.flixel.FlxGame;

class Main extends Sprite 
{
  
	public function new () 
	{
		super();
		
		if (stage != null) 
			init();
		else 
			addEventListener(Event.ADDED_TO_STAGE, init);
	}
	
	private function init(?e:Event = null):Void 
	{
		if (hasEventListener(Event.ADDED_TO_STAGE))
		{
			removeEventListener(Event.ADDED_TO_STAGE, init);
		}
		
		initialize();
		
		var demo:FlxGame = new GameChangerMain();
		addChild(demo);
		
		#if (cpp || neko)
		Lib.current.stage.addEventListener(KeyboardEvent.KEY_UP, onKeyUP);
		#end
	}
	
	#if (cpp || neko)
	private function onKeyUP(e:KeyboardEvent):Void 
	{
		if (e.keyCode == Keyboard.ESCAPE)
		{
			Lib.exit();
		}
	}
	#end
	
	private function initialize():Void 
	{
		Lib.current.stage.align = StageAlign.TOP_LEFT;
		Lib.current.stage.scaleMode = StageScaleMode.NO_SCALE;
	}
	
	// Entry point
	public static function main() {
		
		Lib.current.addChild(new Main());
	}
	
}