threatmap fix null pointer exception when no play services are installed

src/de/tudarmstadt/informatik/hostage/ui/fragment/ThreatMapFragment.java

@@ -434,12 +434,16 @@ public class ThreatMapFragment extends TrackerFragment implements GoogleMap.OnIn
 	@Override
 	public void onResume() {
 		super.onResume();
-		mLocationManager.requestLocationUpdates(mLocationProvider, 0, 1000.0f, this);
+		if (mLocationManager != null) {
+			mLocationManager.requestLocationUpdates(mLocationProvider, 0, 1000.0f, this);
+		}
 	}
 
 	@Override
 	public void onPause() {
 		super.onPause();
-		mLocationManager.removeUpdates(this);
+		if (mLocationManager != null) {
+			mLocationManager.removeUpdates(this);
+		}
 	}
 }