Handle location disabled error
Context: https://gitlab.gnome.org/GNOME/fractal/-/merge_requests/1068#note_1428838
When we try to share our location and the location services are disabled in the settings, we get this error:
Failed to send location ZBus Error: org.freedesktop.portal.Error.NotAllowed: Location services disabled
We should show a custom error message in that case, so the user knows that they have to enable it.
It's currently not possible because we don't get the proper error type, see ashpd#59.