How add "Any" in search module in category fields

Hello
thank you for your component
could you pls help me

Hi,
The search module use "Multiple select list" for Category field. So why do you want to have option "Any"?
Thanks
Dam

i know
but my customer want make that field not bigger than others and without multiple choice (attach).
If i delete "multiple" attribute in (static function listCategories - helper.php) and then use that search module, this field have by default one of category listing and i cant search by all categories

sorry for my english and my question)

Denis