XPTable - advanced data grid

1. Add rows to a table so that the vertical scroll bar becomes visible.
2. Use the scroll bar to scroll all the way to the bottom so that the last
row is visible.
3. Delete all the rows. The rows have to be deleted one at a time to
reproduce this bug e.g.
table1.TableModel.Rows.RemoveAt(i);
4. Add similar number of rows as in Step 1.
5. Use the scroll bar to scroll all the way to the top.
6. Notice that you can no longer scroll to the first row. The scroll bar
gets stuck halfway to the top.