[BUGFIX] Display error icon in folder field

Resolves: #103221
Releases: main, 12.4
Change-Id: I4089a733f9ce2c888c05a4f1e4f7834a00ad1bfc
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/83154
Reviewed-by: Till Hörner <thoerner@3pc.de>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>

typo3/sysext/backend/Classes/Form/Element/FolderElement.php

@@ -260,7 +260,7 @@ public function render(): array
         $html[] = '</div>';
 
         $resultArray['html'] =
-            '<typo3-formengine-element-folder recordFieldId="' . htmlspecialchars($fieldId) . '">
+            '<typo3-formengine-element-folder class="formengine-field-item" recordFieldId="' . htmlspecialchars($fieldId) . '">
                 ' . implode(LF, $html) . '
             </typo3-formengine-element-folder>';