[TASK] Fallback to english template if no other exists

Classes/Service/MailTemplateService.php

@@ -202,6 +202,12 @@ class MailTemplateService {
 			$this->extensionKey, $this->templateName, $this->language
 		)->getFirst();
 
+		// If there is no template for this language, use the english template
+		if ($template === NULL && $this->language !== 'en') {
+			$this->setLanguage('en');
+			$this->sendEmail();
+		}
+
 		if ($template === NULL) {
 			return FALSE;
 		}