sometimes adding/removing languages empties app list

• Device OS and version: LineageOS 14.1.1
• Device model/manufacturer: OnePlusX
• F-Droid version (in the About screen): 1.5.1 (but also verified with current master)
• F-Droid privileged extension version (if installed): no

What did you do? (clear steps if possible)

• Have and up-to-date f-droid index
• Have only English (US) as language
• Add German as second language
• might need some more adding removing of languages as it sometimes works correctly, sometimes it doesn't

What did you expect to see?

• F-Droid triggering an index update

What did you see instead?

• F-Droid connecting to f-droid.org then either aborting, or deciding it doesn't need to download anything.
• Emtpy app list is diplayed.