Bug 1090043 - [B2G][Message] MMS attachments missed in SMIL could not be displayed

- Check if the attachment count match the SMIL and force to parse without SMIL if the count is unmatched
- Make sure mimetype 'application/***' is visible in thread (parseWithoutSMIL case) 
nit: add a mime type that would trigger null (for example: "multipart/form-data")