Visible modal windows and dropdowns crashing game on exit

Opening a modal window and closing the game will crash the game when you exit if you don't close the window first.

Seems to be not just limited to that either, crash on exit will also occur when you have a dropdown menu visible, e.g. the reflection options in the in-game settings window.

Easiest way to reproduce:

1. Kill yourself to be prompted with a modal window
2. Quit the game with the window still open

Tested on master: 4db2f79a