fix problem undefined index

extension/Classes/Core/Report/SendMail.php

@@ -67,7 +67,9 @@ class SendMail {
         if (!empty($redirectAllMail)) {
 
             foreach ([SENDMAIL_TOKEN_RECEIVER, SENDMAIL_TOKEN_RECEIVER_CC, SENDMAIL_TOKEN_RECEIVER_BCC] as $key) {
-                $mailConfig[$key] = (strlen($mailConfig[$key]) > 1023) ? str_replace(',', ', ', $mailConfig[$key]) : $mailConfig[$key];
+                if (isset($mailConfig[$key])) {
+                    $mailConfig[$key] = (strlen($mailConfig[$key]) > 1023) ? str_replace(',', ', ', $mailConfig[$key]) : $mailConfig[$key];
+                }
             }
 
             $addBody = "All QFQ outgoing mails are caught and redirected to you." . PHP_EOL . "Original receiver(s) are ..." . PHP_EOL;