every time I shoot a smaller yellow ball the game freezes plz help, source code:http://www.greenfoot.org/scenarios/6065


public AstroBall(int direction, int health, Counter pointCounter) { setRotation(direction); hp=health; getImage().scale(getImage().getWidth()-health,getImage().getHeight()-health); counter = pointCounter; }
//in the method destroy; if(nhp<50){ getWorld().addObject(new AstroBall(315, nhp, counter),getX()+10,getY()-10); getWorld().addObject(new AstroBall(45, nhp, counter),getX()+10,getY()+10); getWorld().addObject(new AstroBall(135, nhp, counter),getX()-10,getY()+10); getWorld().addObject(new AstroBall(225, nhp, counter),getX()-10,getY()-10); }