I need some help with a java program I'm writing (SOLVED) [GA inside, still running]

Hello all. So I'm currently in the process of writing a little java program and I'm getting a NullPointerException and I have no idea why it's giving me it. I know what it means, but as far as I can see, it shouldn't happen.

Here's a (very) small part of my code (of my Game class):

private GUIHandler handler;
handler = new GUIHandler(this);

And the constructor of GUIHandler:

public GUIHandler(Game game)
{
System.out.println(game);
this.game = game;
}

I think this is where it throws the error (discovered that by printing a lot to the console (basically before every statement) and then checking where it happened), but I have no idea why. Does anyone have any idea?

I know this is not the most optimal place to ask, but I know that there are quite a few people here that might be able to help me and I really just needed an excuse to make a forum GA. :p

https://www.steamgifts.com/giveaway/CHwhA/chroma-squad

EDIT: nevermind, I'm an idiot. I forgot to initialize an ArrayList...
I feel so stupid now...