[send CLAIM_DEF] Claim DEF was published when it should not have been

Build Info:
sovrin-client 0.4.19
sovrin-node 0.4.9

Overview:
Exceptions are raised due to command execution.

Steps to Reproduce - Case 1:
1. Send CLAIM_DEF with nonexistent seqNo as REF parameter.

Actual Results:
Task exception was never retrieved
future: <Task finished coro=<SovrinCli._sendClaimDefActionAsync() done, defined at /usr/local/lib/python3.5/dist-packages/sovrin_client/cli/cli.py:737> exception=AttributeError("'NoneType' object has no attribute 'issuerId'",)>

Expected Results:
User-friendly error message about incorrect REF parameter.

Steps to Reproduce - Case 2:
1. Send CLAIM_DEF with existing seqNo as REF parameter.

Actual Results:
The following claim definition is published to the Sovrin distributed ledger
...
Task exception was never retrieved
future: <Task finished coro=<SovrinCli._sendClaimDefActionAsync() done, defined at /usr/local/lib/python3.5/dist-packages/sovrin_client/cli/cli.py:737> exception=AttributeError("'tuple' object has no attribute 'seqId'",)>

Expected Results:
There should be no error or exception messages because the claim definition is successfully published.