Fixed bugs in theme options and admin panel

【Contents of fixes and feature additions】
■Fixed a bug that an error message is displayed on the admin screen when the logo image for PC is deleted while leaving the logo image for smartphone.
■Fixed a bug that an error message was displayed in the article list on the admin screen with PHP 5.6 or later.
■Added the ability to hide pictograms.

The following are the files that have been modified for this update.
【Corrected files】
admin/theme-options.php
functions.php
languages/default.mo
languages/default.po
languages/ja.mo
languages/ja.po
style.css

For more information, please visit the IZM (tcd034) download site for purchasers.