getStoreValuesForForm($empty = false, $all = false) has bad logic (undefine variable)

Author: edenduong

app/code/Magento/Store/Model/System/Store.php

@@ -3,6 +3,9 @@
  * Copyright © Magento, Inc. All rights reserved.
  * See COPYING.txt for license details.
  */
+
+declare(strict_types=1);
+
 namespace Magento\Store\Model\System;
 
 use Magento\Framework\Data\OptionSourceInterface;
@@ -126,7 +129,7 @@ public function getStoreValuesForForm($empty = false, $all = false)
                 if ($website->getId() != $group->getWebsiteId()) {
                     continue;
                 }
-                $groupShow = false;
+                $values = [];
                 foreach ($this->_storeCollection as $store) {
                     if ($group->getId() != $store->getGroupId()) {
                         continue;
@@ -135,16 +138,12 @@ public function getStoreValuesForForm($empty = false, $all = false)
                         $options[] = ['label' => $website->getName(), 'value' => []];
                         $websiteShow = true;
                     }
-                    if (!$groupShow) {
-                        $groupShow = true;
-                        $values = [];
-                    }
                     $values[] = [
                         'label' => str_repeat($nonEscapableNbspChar, 4) . $store->getName(),
                         'value' => $store->getId(),
                     ];
                 }
-                if ($groupShow) {
+                if (!empty($values)) {
                     $options[] = [
                         'label' => str_repeat($nonEscapableNbspChar, 4) . $group->getName(),
                         'value' => $values,