Opp: Do not terminate session when a Batch contains an empty file

Use Case:
1) pair to remote device.
2) Send files in a batch, such that the batch
   contains an empty file in between.

Failure:
Remote rejects empty file and DUT stop sending remaining
files in queue

Fix:
If an empty file is rejected by the remote device, client session is
terminated and remaining files in the batch also marked as failure.
This change continues to send the pending files in the batch even an
empty file is rejected by the remote device. Also it provides appropriate
message to the user.

CRs-Fixed: 1019540
Change-Id: I90d06ad9f21ae387e38f076c0f16ce1d05bdf7ea