grouped column header don't show when unhide columns

[interloper10]

I have a grid with column groups like:
http://paramquery.com/pro/demos/group_columns

I also have a toolbar with widget to hide/unhide columns like:
http://paramquery.com/pro/demos/showhide_columns

It seems that if I unhide a column that is default hidden (default hidden: true in column), the column will show but the column grouping doesn't reflect column model for the grouped column. 
Is there anyway to refresh the columnModel or header.

I tried refereshHeader on the show/hide column change listener.

[paramvir]

colModel can be refreshed as

Code: [Select]

grid.option( "colModel", grid.option( "colModel" ) ); //refresh colModel
grid.refresh(); //and refresh the grid.