Launching Settings app resets theme selected in GNOME Tweaks to Pop!_OS theme

[aral]

To reproduce

1. Select Dark Mode in the Settings app
2. Set Adwaita Dark in GNOME Tweaks
3. Launch settings

What should happen

Nothing.

What actually happens

Theme reverts to Pop!_OS Dark.

[jackpot51]

I believe this is a problem in theme-switcher so I have transferred the issue there