Avoid having left/right buttons jump back and forth

Set a min width so that once it has grown it can't get smaller again.

android_app/app/src/main/java/com/health/openscale/gui/activities/DataEntryActivity.java

@@ -328,6 +328,7 @@ public class DataEntryActivity extends AppCompatActivity {
             measurement.loadFrom(scaleMeasurement, previousMeasurement);
         }
 
+        txtDataNr.setMinWidth(txtDataNr.getWidth());
         txtDataNr.setText(DateFormat.getDateTimeInstance(
                 DateFormat.LONG, DateFormat.SHORT).format(scaleMeasurement.getDateTime()));
     }