Darkmode is broken, different behavior in settings dialog with OK/Cancel.

[ikbenkous]

Steps to enable bug:

1. Go to settings
2. Enable darkmode by pressing the "Darkmode" button once
3. Observe program correctly switching to darkmode theme.
4. Press "OK".
5. Observe program now switching back theme to light mode yet the setting internally is correctly saved as "darkmode enabled"

Steps to observe weird behavior:

1. With darkmode internally enabled, open settings dialog.
2. Observe how program switches the theme between light/dark.
3. Press cancel to preserve this new theme.
4. Repeat this process to toggle it back again.

You can keep opening the settings and pressing cancel to get this to flip over and over again.

SetupPageColors::setDarkMode(bool) correctly applies the palette so I have no idea where this odd behavior is coming from.