Bugfix: speed and altitude were set to 0m repeatedly (UI only. Data is okay).

Fixes #2258.

src/main/java/de/dennisguse/opentracks/sensors/SensorManager.java

@@ -126,6 +126,7 @@ public class SensorManager implements SharedPreferences.OnSharedPreferenceChange
         gpsHandler.resetAggregated();
     }
 
+    @VisibleForTesting
     public GpsHandler getGpsHandler() {
         return gpsHandler;
     }