Fixed multiple bugs

【Contents of the fix】
■Fixed an issue where the text color and background color could not be changed in the “Schedule Content Settings” of the “Staff” custom post type.
■Fixed a bug that images are not displayed only on pages created with the fixed page template “Fixed Page for LP” 【IE】.
■Fixed a bug that the overlay color setting of TCD theme option “Staff” is not reflected in the schedule image.
■Fixed a bug where an error would occur when you clicked on the preview button in the Testimonials section.

【Modified file】
functions/head.php
functions/staff_cf.php
single-staff.php
single-voice.php
style.css