Fatal error: Uncaught Error: Call to undefined function add_filter() in /users/laufgruppe-lvb/www/wordpress/wp-content/plugins/so-widgets-bundle/icons/materialicons/filter.php:10 Stack trace: #0 {main} thrown in /users/laufgruppe-lvb/www/wordpress/wp-content/plugins/so-widgets-bundle/icons/materialicons/filter.php on line 10