mapView: Don't set dark background pattern when wrapping

The wrapping code in libchamplain seems to be broken
when setting a background pattern.
As a work-around, disable the custom dark background
pattern when using the dark them if the view is wrapping
around between 180 and -180 degrees longitude.
1 job for wip/mlundblad/fix-wrap-background in 8 minutes and 16 seconds (queued for 1 second)