Apply patch attached to issue2550937 traceback/crash due to passing

empty sendto to smtp_send. Fix by Trent Gamblin.

http://issues.roundup-tracker.org/issue2550937

Author: rouilj

CHANGES.txt

@@ -424,6 +424,9 @@ Fixed:
   permissions check was changed to require that the user have View
   access to the labelprop for the class rather than View access to the
   class. (John Rouillard)
+- issue2550937: fix crash by verifying that sendto is not null before
+  calling mailer.smtp_send. Discovered and patched by Trent Gamblin.
+  Applied by John Rouillard.
 
 2016-01-11: 1.5.1
 

roundup/roundupdb.py

@@ -658,7 +658,8 @@ def send_message(self, issueid, msgid, note, sendto, from_address=None,
                 if message.get ('In-Reply-To'):
                     send_msg ['In-Reply-To'] = message ['In-Reply-To']
 
-            mailer.smtp_send(sendto, send_msg.as_string())
+            if sendto:
+                mailer.smtp_send(sendto, send_msg.as_string())
             if first:
                 if crypt:
                     # send individual bcc mails, otherwise receivers can