ListBox PaintCellBackground now paints the empty area below the last row, matching Xojo

ListBox.PaintCellBackground fills only the rows that exist, instead of the whole ListBox content area. In Xojo, PaintCellBackground fires for every visible cell, including the empty cells below the last row, so filling 0, 0, g.Width, g.Height colours the entire ListBox background. In Objo the same code colours only the actual rows, leaving the empty area below them unpainted.

Expected behaviour: the whole ListBox background is now painted, matching Xojo.