[TASK] Prevent empty marker label

Classes/Service/MailTemplateService.php

@@ -846,9 +846,10 @@ class MailTemplateService {
 		$allMarker = '';
 
 		foreach ($markers as $key => $value) {
-			if (\array_key_exists($key, $this->markerLabels)) {
+			if (\array_key_exists($key, $this->markerLabels) && $this->markerLabels[$key] !== NULL) {
 				$key = $this->markerLabels[$key];
 			}
+
 			if (\is_string($value)) {
 				$allMarker .= $key . ': ' . $value . PHP_EOL;
 			} elseif (\is_array($value)) {

Classes/XClass/Form/FormEditorController.php

@@ -150,11 +150,7 @@ class FormEditorController extends \TYPO3\CMS\Form\Controller\FormEditorControll
 				$markerName = $markerArray[0];
 			}
 			$markerName = RegisterService::normalizeFormFieldMarkerName($markerName);
-
-			$markerLabel = $markerArray[0];
-			if (isset($markerArray[1])) {
-				$markerLabel = $markerArray[1];
-			}
+			$markerLabel = $markerArray[1] ?? $markerArray[0];
 			$markers[$markerName] = [
 				'identifier' => $markerName,
 				'type' => MailTemplateService::MARKER_TYPE_STRING,