AdvColumnGrid Alternate Row bug

Hi, 

I've noticed a bug when upgrading and application.
It occurs when you have more than one fixed row and merged cells in header.

Steps to reproduce:
- Add a AdvColumnGrid
- Bands.Active := TRUE
- ShowBands := TRUE for each column
- FixedRows := 2;
- in code :
  MergeCells(0,0,2,1);

https://pasteboard.co/IfqUdej.png