MDL-83550 gradingform_rubric: fix submit no grade when remark disabled

grade/grading/form/rubric/renderer.php

@@ -115,6 +115,16 @@ class gradingform_rubric_renderer extends plugin_renderer_base {
             $descriptiontdparams['aria-label'] = get_string('criterion', 'gradingform_rubric', s($criterion['description']));
         }
 
+        // Default value for criterion ids.
+        // Edge case: submitting empty grade when remark field is disabled.
+        // Reason: we need the criteria keys for the clear_attempt to clear the rubric fillings.
+        if ($mode == gradingform_rubric_controller::DISPLAY_EVAL) {
+            $criteriontemplate .= html_writer::empty_tag('input', [
+                'type' => 'hidden',
+                'name' => '{NAME}[criteria][{CRITERION-id}][]',
+            ]);
+        }
+
         // Description cell.
         $criteriontemplate .= html_writer::tag('td', $description, $descriptiontdparams);