Fix when the course has not gradebook - refs BT#9889 #TMI

main/gradebook/lib/be/category.class.php

@@ -2029,6 +2029,10 @@ class Category implements GradebookItem
                 false
             );
 
+            if (empty($cats_course)) {
+                return false;
+            }
+
             $category = $cats_course[0];
         }
 
@@ -2093,6 +2097,10 @@ class Category implements GradebookItem
             false
         );
 
+        if (empty($cats_course)) {
+            return 0;
+        }
+
         $category = $cats_course[0];
 
         $courseEvaluations = $category->get_evaluations($userId, true);