MDL-80302 completion: Improve default completion error tracking

Co-authored-by: Sara Arjona <[email protected]>

completion/classes/edit_base_form.php

@@ -109,10 +109,15 @@ abstract class core_completion_edit_base_form extends moodleform {
         $component = "mod_{$modnames[0]}";
         $itemnames = \core_grades\component_gradeitems::get_itemname_mapping_for_component($component);
         $hascustomrules = count($itemnames) > 1;
+        $customcompletionelements = [];
 
         try {
             // Add completion rules from the module form to this form.
             $moduleform = $this->get_module_form();
+            // If the module doesn't return a form for any reason, we don't continue checking.
+            if (!$moduleform) {
+                return [false, []];
+            }
             $moduleform->_form = $this->_form;
             if ($customcompletionelements = $moduleform->{$function}()) {
                 $hascustomrules = true;
@@ -135,7 +140,7 @@ abstract class core_completion_edit_base_form extends moodleform {
         } catch (Exception $e) {
             debugging('Could not add custom completion rule of module ' . $modnames[0] .
                 ' to this form, this has to be fixed by the developer', DEBUG_DEVELOPER);
-            return [$hascustomrules, $customcompletionelements];
+            return [false, $customcompletionelements];
         }
     }