Cannot store preferences anymore
I am not able to store my settings anymore.

Git version 00dfb2fee43e2999b00d06f7aaf5871659d08cd0
- select preferences
- change parameters (e. g: nitter.com -> own.serv.er, invidious.com -> own.vidserv.er, change theme to twitter)
- click save preferences

Expected: Page should minimum show the twitter theme
Actual behaviour:
- nitter page has still nitter theme
- when selecting preferences all old parameters (e.g. nitter.com...) are set, no new settings anymore

This was tested with firefox (76.0.1 with my normal profile and - of course a new clean one), 
chromium (clean). Sometimes I can see the twitter theme for one, two pages. More interesting: RSS feeds (old ones too) now link e.g. to nitter.com and not to my own server.
