Update js/grid.custom.js

Changing the lines 198 from "$(rows.namedItem(id)).css("display","");" to "$('#'+id,'#'+$t.id+'_frozen, #'+$t.id).css("display","");" I was able to set frozen columns on treegrid. I´ve done the same on the collapseRow function. I have to change too the grid.custom.js to enable the feature.