Level boundary query

The problem is in your mario class. The method boundary() checks whether mario reaches the end of the level. If he reaches it the method setupLevel(int) int Level is executed which removes all objects from the world. So your mario get's removed from the world. But after removing your mario from the world the act method needs to be executed till the end. So after the execution of the method boundary() your checkGround() method is executed. This method uses the getOneObjectAtOffset method. And to execute this method your actor needs to be in the world. To fix this problem you could check if mario is still in the world before executing the checkGround() method.