Fixes picking an avatar image on Android.
- Choosing a profile picture works on Android again. The avatar picker
used the system file chooser, which hands back a reference the app cannot
actually read — so the image never appeared and you got a "read image"
error instead. It now uses the same in-app file browser every other picker
in the app already used, which is why uploads worked while this did not.
Thanks to the reporter on issue #278.