Fix for custom repo-uri

[dreadnought]

A kismon user reported that setting a custom tile URL doesn't work any more. I've traced the issue down to 05d9ea1ad15e5a06ecd1dd357120b8374855665d, where the default map_source value was changed from -1 to 0. Since then map_source is OSM_GPS_MAP_SOURCE_NULL when the map gets initialized with a custom repo-uri and loads osm_gps_map_blit_tile instead of the right tiles.

While testing it, I've noticed another issue in the mapviewer.py: Clicking on the on the Load Map URI button under the Map Repository URI option throws an error that says that self.map_clicked doesn't exist. The function was removed a long time ago and connecting the event is no longer necessary.

To reproduce the issue:

• Apply the change to the mapviewer.py and launch it
• Click the Load Map URI button and the map turns gray
• Close mapviewer.py, apply the changes to osm-gps-map-widget.c and rebuild it
• Click the Load Map URI button and the map remains.

[dreadnought]

The CI test fails because of issues with the Ubuntu repository. They seem to be unrelated to the patch or this project.

[johnny-bit]

THANKS!

Seems like CI on GH is having troubles. I tried to restart it couple times to no avail. Merged since fix looks absolutely 100% correct.