MMS: Fix issue that backup MMS from operators failed.

When receiving MMS from operators server number, it will save
 in part table with both name and content location as null.

Add the check of content ID when making the PDU body, so as
 to make sure either the name, file name, content location/ID
 of the PDU part is not null. Otherwise, return ERROR.

Change-Id: Ie8067c4abc4e52d70d11b8c7b615d2664353ba5a
CRs-Fixed: 650563