Cleanup: SegmentStatisticUpdater.

src/main/java/de/dennisguse/opentracks/stats/TrackStatisticsUpdater.java

@@ -214,11 +214,12 @@ public class TrackStatisticsUpdater {
         }
     }
 
-    @NonNull
     @Override
     public String toString() {
         return "TrackStatisticsUpdater{" +
-                "trackStatistics=" + segmentStatisticUpdater +
+                "segmentStatisticUpdater=" + segmentStatisticUpdater +
+                ", currentSegment=" + currentSegment +
+                ", lastTrackPoint=" + lastTrackPoint +
                 '}';
     }
 }