When gps is disabled, clear the current location.

MyTracks/src/com/google/android/apps/mytracks/content/TrackDataHub.java

@@ -686,6 +686,7 @@ public class TrackDataHub implements DataSourceListener {
     TrackDataListener.LocationState locationState;
     if (!hasProviderEnabled) {
       locationState = LocationState.DISABLED;
+      lastSeenLocation = null;
     } else if (!hasFix) {
       locationState = LocationState.NO_FIX;
     } else if (!hasGoodFix) {

MyTracks/src/com/google/android/apps/mytracks/fragments/MapFragment.java

@@ -289,6 +289,8 @@ public class MapFragment extends Fragment
                     : R.string.gps_location_access);
             message = getString(R.string.gps_disabled, setting);
             isGpsDisabled = true;
+            currentLocation = null;
+            updateCurrentLocation();
             break;
           case NO_FIX:
             message = getString(R.string.gps_wait_for_signal);