Fix setting of wrong (0, 0) location if the location is missing

Signed-off-by: Leandro Lucarella <[email protected]>

Author: llucax

src/frequenz/client/microgrid/_client.py

@@ -203,7 +203,7 @@ async def metadata(self) -> Metadata:
             return Metadata()
 
         location: Location | None = None
-        if microgrid_metadata.location:
+        if microgrid_metadata.HasField("location"):
             location = Location(
                 latitude=microgrid_metadata.location.latitude,
                 longitude=microgrid_metadata.location.longitude,