mms: fix NPE in compose message activity onStart when in multi select mode

Change-Id: Icc522abbba6f7abf5e80f294ef18466de3345836
Mms: Add to no subject filter for mms messages

* Some carriers add a default subject if one is not provided.
* T-Mobile US adds NoSubject if no subject is added.

Change-Id: Ibed4383d33c24922bcf758862f5e0a9f0e3ed97c