Fix «Dispose the telemetry map controller on widget teardown»

lib/widgets/telemetry_location_map.dart

@@ -41,6 +41,12 @@ class _TelemetryLocationMapState extends State<TelemetryLocationMap> {
 
   LatLng get _position => LatLng(widget.latitude, widget.longitude);
 
+  @override
+  void dispose() {
+    _mapController.dispose();
+    super.dispose();
+  }
+
   @override
   void didUpdateWidget(covariant TelemetryLocationMap oldWidget) {
     super.didUpdateWidget(oldWidget);