To reproduce:

1. Create new project
2. In Player Settings, set Graphics API to OpenGLCore
3. Build standalone project
4. Run project
5. In Launcher, set resolution to different than the monitors' resolution
6. Set windowed to false
7. Close the game with ALT + F4

Expected: playing the game, which was built with Graphics API set to OpenGLCore should not crash the game, if it has been set to fullscreen with some other resolution than the native resolution of the monitor and you quit from the game using ALT + F4

Actual: playing the game, which was built with Graphics API set to OpenGLCore crashes the game, if it has been set to fullscreen with some other resolution than the native resolution of the monitor and you quit from the game using ALT + F4

Reproduced in 5.5.2p4, 5.5.3f1, 5.6.0f3, 5.6.0p1, 2017.1.0b1