Polygrid columns not fully clearing when pgColumns is set

[Paul Dupuis]

Hi to any polygrid developers out there,

Please see bug https://quality.livecode.com/show_bug.cgi?id=24315

I have run into an issue with the latest polygrid (as of this post) 
where if you set pgColumns to a new array that reduces the number of 
columns in the grid, some old columns are not cleared, but instead are 
set to defaults (ie. the names revert to col5, col6, etc. instead of 
being completely removed

Any thoughts to a work-around?