Fatal error: Uncaught Error: Class 'IS_Loader' not found in /var/www/wp-content/plugins/add-search-to-menu/add-search-to-menu.php:173 Stack trace: #0 /var/www/wp-content/plugins/add-search-to-menu/add-search-to-menu.php(183): Ivory_Search->start() #1 /var/www/wp-includes/class-wp-hook.php(303): ivory_search_start('') #2 /var/www/wp-includes/class-wp-hook.php(327): WP_Hook->apply_filters(NULL, Array) #3 /var/www/wp-includes/plugin.php(470): WP_Hook->do_action(Array) #4 /var/www/wp-settings.php(441): do_action('plugins_loaded') #5 /var/www/wp-config.php(107): require_once('/var/www/wp-set...') #6 /var/www/wp-load.php(50): require_once('/var/www/wp-con...') #7 /var/www/wp-blog-header.php(13): require_once('/var/www/wp-loa...') #8 /var/www/index.php(17): require('/var/www/wp-blo...') #9 {main} thrown in /var/www/wp-content/plugins/add-search-to-menu/add-search-to-menu.php on line 173