mapView: Don't try to set aerial tiles if not available

Safe-guard agains setting the aerial tile source
if it's not available in the service file.
This avoid a crash if aerial was saved as last-used
map type in gsettings and at next startup the service
has dropped support.
1 job for wip/mlundblad/fix-saved-aerial-no-support in 9 minutes and 41 seconds
latest
Status Job ID Name Coverage
  Test
passed flatpak #1324044
flatpak

00:09:41