* Do not send mails, if the "To:" address is empty, might happen

if authors do not have a mail account entered in their profile.
      (nealk)

include/functions.inc.php

@@ -541,7 +541,7 @@ function serendipity_sendMail($to, $subject, $message, $fromMail, $headers = NUL
         fclose($fp);
     }
 
-    if (!isset($maildata['skip_native'])) {
+    if (!isset($maildata['skip_native']) && !empty($maildata['to'])) {
         return mail($maildata['to'], $maildata['subject'], $maildata['message'], implode("\n", $maildata['headers']));
     }
 }