Bugfix: reset user selected data when user changes

... otherwise if user A selects data on the line chart,
and switches to user B, user B sees the selected data
of user A instead of user B's last data.

android_app/app/src/main/java/com/health/openscale/gui/OverviewFragment.java

@@ -224,6 +224,8 @@ public class OverviewFragment extends Fragment implements FragmentUpdateListener
 
         currentScaleUser =  OpenScale.getInstance(overviewView.getContext()).getSelectedScaleUser();
 
+        userSelectedData = null;
+
         measurementWeightLast.scaleUser = currentScaleUser;
         measurementBMILast.scaleUser = currentScaleUser;
         measurementWaterLast.scaleUser = currentScaleUser;