Fix route calculation error when no route has been found

lib/src/directions_repository.dart

@@ -6,7 +6,7 @@ class DirectionsRepository {
   static const String _baseUrl = '/maps/api/directions/json';
 
   /// get the route between the two coordinates
-  Future<Directions> getDirections({
+  Future<Directions?> getDirections({
     required LatLng origin,
     required LatLng destination,
     required TravelMode mode,
@@ -32,7 +32,11 @@ class DirectionsRepository {
         },
       );
       if (response.statusCode == 200) {
+        try {
           return Directions.fromMap(jsonDecode(response.body));
+        } on GoogleMapsException catch (_) {
+          return null;
+        }
       }
     } on HttpException catch (e) {
       debugPrint(e.message);

lib/src/google_map.dart

@@ -237,17 +237,20 @@ class _GoogleTrackTraceMapState extends State<GoogleTrackTraceMap> {
             key: widget.googleAPIKey,
           )
           .then(
-            (value) => {
+            (Directions? directions) => {
+              if (directions != null)
+                {
                   controller.route = TrackTraceRoute(
-                value.totalDuration,
-                value.totalDistance,
-                value.polylinePoints,
+                    directions.totalDuration,
+                    directions.totalDistance,
+                    directions.polylinePoints,
                   ),
                   checkDestinationCloseBy(),
                   controller.recenterCamera(),
                   setState(() {
                     lastRouteUpdate = DateTime.now();
                   }),
+                }
             },
           );
     }