praekelt/vumi — pull request #810 by smn (2014-05-30 15:34:17+00:00)
Title: Sometimes an MNO sends us a None and we just have to accept it.

Currently when an MNO sends us `deliver_sm` with `short_message: None` we always reply with `ESME_RDELIVERYFAILURE.`.

With a certain MNO this response results in them no longer sending us _any_ `deliver_sm`s.