The summary of this bug is summed up in the title.

What I expected to happen was...: The ability to press "Respawn" or "Title Screen" on the death screen after switching from fullscreen to windowed or the other way around,

What actually happened was...: The buttons that you would usually press were stuck on the dark grey color that indicates that they are not available to press.

Steps to Reproduce:
1. Open minecraft and join any world.
2. Die within the game in any way. Just to get to the "You died!" screen.
3. Switch from full-screen to windowed or the other way around via pressing the F11 key (or whichever key is assigned to 'fullscreen mode').