Fix class loading bug #20

Author: brendanheywood

classes/local/hook/output/before_standard_head_html_generation.php

@@ -34,7 +34,9 @@ class before_standard_head_html_generation {
      * @param \core\hook\output\before_standard_head_html_generation $hook
      */
     public static function callback(\core\hook\output\before_standard_head_html_generation $hook): void {
-        GLOBAL $PAGE;
+        global $PAGE, $CFG;
+
+        require_once($CFG->dirroot . '/admin/tool/seo/lib.php');
 
         // If URL should not be indexed, add the noindex meta tag to page.
         if (seo::is_url_indexable($PAGE->url->get_path()) == false) {