[0.16.1390]Revert & keep buttons show no functionality when upscaling resolution

[jacko21297]

Attempting to upscale the resolution whilst in 'Windowed Fullscreen' mode will prevent the 'Revert' or 'Keep' button's from showing functionality.

Steps To Reproduce:
1. Load RimWorld Version '0.16.1390'.
2. Ensure that the 'Fullscreen' option is unticked.
3. Drag the Window to the top of the screen to make it 'partially fullscreen'.
4. With the options menu open, change the resolution to a value greater than the one it currently resides in.

Actual Result:
Note how the 'Revert' or 'Keep' button's will show no functionality.

Expected Result:
Both of the aforementioned buttons should always show functionality.

[Tynan]

Assuming "show functionality" actually means "be on screen", we can't guarantee they will be visible, which is why there is a countdown timer to revert.