GDK: Press Alt+F4 can only pause the game while in a world.

Steps to reproduce this issue:

1. Enter a world, make sure that the game is not paused, and no GUI is open.

2. Press Alt+F4 for once.

Expected result:

The game will close when you press Alt+F4.

Actual result:

It only pauses the game; you will have to press them again in order to close the game.