This error occurred simply closing the game. Anytime I leave the game window I get an error.

Put the summary of the bug you're having here

What I expected to happen was...:
Save and exit.

What actually happened was...:
Game froze up and got a not responding message on the application window that did not end. Eventually I just decided to try to close the window and got this error.

Steps to Reproduce:
1. Start a game.
2. Save and Exit.
3. Get the error.