Mail with no Subject line causes DOS

[Kevin-myer]

One of the fixes for 2.0.14 included some patches to
the way Mailman/MailCommandHandler.py handles the
subject line. After applying this patch to 2.0.13, I
found that if a message is sent to a list that contains
no Subject: line in the header, all processing of
messages stops. Once I clear out that particular
message, the queue processing starts again.

Note: Its not a blank Subject: line thats causing this
problem - its a message without a Subject: line at all.
 Maybe its coincidental and not related to the patch I
applied for 2.0.14 but the timing it too close to be
not related somehow.

[http://sourceforge.net/tracker/index.php?func=detail&aid=940386&group_id=103&atid=100103]