Multiple bug fixes

【Contents of the fix】
■Fixed an error that was sometimes displayed on 404 pages.
■Fixed a bug that the layout may be broken when the search widget is placed on the right side.
■Fixed an error that sometimes appears in the theme options screen.

The following files have been modified for this update.
【Fixed files】
admin/theme-options.php
404.php
style.css
style_pc.css

For more information, please visit the download site for the purchaser of Opinion (tcd018).