Fatal error: Uncaught Error: call_user_func_array(): Argument #1 ($callback) must be a valid callback, class WPViralQuizGR does not have a method "create_thumbnail"
in /data02/virt28050/domeenid/www.bestor.ee/htdocs/loosike/wp-includes/class-wp-hook.php on line 292

Call stack:

1. WP_Hook::apply_filters()
   wp-includes/class-wp-hook.php:316
2. WP_Hook::do_action()
   wp-includes/plugin.php:484
3. do_action()
   wp-settings.php:538
4. require_once()
   wp-config.php:92
5. require_once()
   wp-load.php:37
6. require_once()
   wp-blog-header.php:13
7. require()
   index.php:17