[BUFIX] Fix issue with non-array marker assignment

Classes/Service/MailTemplateService.php

@@ -351,7 +351,7 @@ class MailTemplateService {
 	public function setMarkers(array $markers): MailTemplateService {
 		$this->markers = $markers;
 		foreach($markers as $key => $currentMarker) {
-			if (!isset($currentMarker['markerLabel'])) {
+			if (!\is_array($currentMarker) || !isset($currentMarker['markerLabel'])) {
 				continue;
 			}
 			$this->markerLabels[$key] = $currentMarker['markerLabel'];