Fixed a bug in the search function

【Contents of the fix】
■Fixed a bug in the category drop-down search 3 (the rightmost search window) that prevented the search from narrowing down properly.
■Adjusted the tablet display.
■Fixed an error that may occur when performing a narrowed search.

The following are the files that have been modified for this update.
【Corrected files】
functions/custom_search.php
custom_search_results.php
style.css