Fixed "grade_item" not found error due to missing required file

Author: mdjnelson

element/grade/classes/element.php

@@ -24,11 +24,15 @@
 
 namespace customcertelement_grade;
 
+defined('MOODLE_INTERNAL') || die();
+
 /**
  * Grade - Course
  */
 define('CUSTOMCERT_GRADE_COURSE', '0');
 
+require_once($CFG->libdir . '/gradelib.php');
+
 /**
  * The customcert element grade's core interaction API.
  *