Fatal error: Uncaught Error: Class "WP_REST_Controller" not found in /var/www/andovercg/staging/wp-content/plugins/ultimate-addons-for-gutenberg/lib/gutenberg-templates/inc/api/api-base.php:16 Stack trace: #0 {main} thrown in /var/www/andovercg/staging/wp-content/plugins/ultimate-addons-for-gutenberg/lib/gutenberg-templates/inc/api/api-base.php on line 16