I use jQuery('#tab').jqGrid('columnChooser', {“msel_opts”: $.ui.multiselect.defaults});
And i replaced destroyed in ui.multiselect like in last OlegK answer.
It's OK even if the modal inputs buttons are very bigs.
In short :
1. use jQuery('#tab').jqGrid('columnChooser', {“msel_opts”: $.ui.multiselect.defaults});
2. change destroy ui.multiselect
3. change code grid.jquery.ui as in my answer 5
I've forgotten anything ?