Game Error Simulation

[Retyping]

Hey Everyone.
I'm trying to create a simple target practice game and I have the targets moving as I want. When I'm trying to establish the 'score' that will also command my program to stop the game crashes.
I have no idea why.

Ultimately, I'd like my objects to go invisible after they've been clicked on so you can gain a point. Once all targets are invisible I'd like to add some text to say you've won. But first, I just want to make sure the game even works. Could someone give me some feedback on how to make this happen?

Thanks!