Disables the built-in Dark theme in Cuztomize section.

[AldegarDespoina]

For some reason the dark theme is disabled in Customize section: https://i.imgur.com/ZJgEiF9.png

OS Used; Windows 7 Home Premium (64bit)
Firefox Version Used: 60 Stable (64bit)

[spikespaz]

I don't actually think I can control this. May be related to #18, not sure though because it IS themed in the default dark mode.

[spikespaz]

Also, I have a question about this on Windows 7. How does it interact with the legacy Aero system that 7 uses? I didn't test for compatibility and I thought #11 would be a problem.

[AldegarDespoina]

It seems it has to do with Windows 7 Aero theme feature or something because when i try to switch to a theme where it doesn't use Aero the Customize section color also changes.