CS-5527: Fixes error when editing slidehows and rich text captions are enabled

PHP Fatal error: Call to undefined function validateTinyMCEEditors() in
/var/www/newscoop/application/modules/admin/views/scripts/slideshow/edit-item.phtml
on line 13
Merge pull request #846 from m038/CS-5527

CS-5527: Fixes error when editing slidehows and rich text captions are e...