weather: Handle GeoClue not responding

If GeoClue is not responding for some reason, the callback of
Geoclue.Simple.new would not get called, meaning that _gclueFailed
remains false. This is preventing the fallback to the most recently
used location in gnome-weather, because it requires _gclueFailed to be
true (or auto-location to be disabled). So neither code path sets a
location and the libgweather default (New York City) is being used
instead.

https://bugzilla.gnome.org/show_bug.cgi?id=779898