Add better SQL exception handling to the Sync framework (see bug #3202693)

- do the reply.writeNoException() only if there are NO exceptions
- before, the code could actually generate an exception when asking for the count or the index,
and then the exception could not be unmaarshalled because we previously calling reply.writeNoException()

Change-Id: I241120878c3fc10fea5fbaeb74f9124b1413a3d4