Fix infinite boot-loop bug in SM.

Bug:11064918
If the ContentResolver sync API is used with the empty ("")
string as a provider, the ContentService will throw an RTE.
This cl addresses all the entry points of the API that could
allow this, as well as adds an ifEmpty check at the point of
failure.
Also removed RTE throws from public functions(no point in
crashing the phone).

Change-Id: I57427d12a6cafb3e6d7a32ca0c10b05315b20580