#34 Fixed selectable are not rendered

[benlei]

If getFixedSelectableRowCount() returns a value greater than 0, these rows are not rendered. In place of these rows, the content of the window behind is shown and vertical scrolling causes the first none fixed row to flicker. Changing the line 675 in getYforRow from if (row < m_Model.getFixedHeaderRowCount()) { to if (row < m_Model.getFixedHeaderRowCount() + m_Model.getFixedSelectableRowCount()) { should solve this problem.