MDL-68733 quiz editing: be more careful deleting random question tags

mod/quiz/editrandom.php

@@ -149,7 +149,7 @@ if ($mform->is_cancelled()) {
     // Now, delete the remaining records.
     if (!empty($recordstokeep)) {
         list($select, $params) = $DB->get_in_or_equal($recordstokeep, SQL_PARAMS_QM, 'param', false);
-        $DB->delete_records_select('quiz_slot_tags', "id $select", $params);
+        $DB->delete_records_select('quiz_slot_tags', "slotid = {$slot->id} AND id $select", $params);
     } else {
         $DB->delete_records('quiz_slot_tags', array('slotid' => $slot->id));
     }

mod/quiz/locallib.php

@@ -2546,7 +2546,7 @@ function quiz_retrieve_tags_for_slot_ids($slotids) {
                 }
             }
 
-            $carry[$slottag->slotid][] = $slottag;
+            $carry[$slottag->slotid][$slottag->id] = $slottag;
             return $carry;
         },
         $emptytagids