Fixing error with some HERE responses

src/traveltime_google_comparison/requests/here_handler.py

@@ -62,6 +62,14 @@ async def send_request(
                         for section in first_route["sections"]
                     )
 
+                    # For some reason, HERE provider returns 0 duration, 0 length
+                    # for some routes in the mountains, but doesn't indicate anywhere
+                    # that it failed. Returning 0 fails `asType(int)` conversion later.
+                    # Example route in UK where this happens:
+                    # "58.61966879999991, -5.0040819999999995","58.578906999999894, -4.880025099999999"
+                    if total_duration == 0:
+                        return RequestResult(None)
+
                     return RequestResult(travel_time=total_duration)
                 else:
                     error_message = data.get("detailedError", "")