Malformed CLI command on no-change transactions

[samuelWilliams99]

If we run a drop with the exact amount of tokens to be distributed, such that the last transaction will not have any "change" of the asset to return back to us, the cli sees a --tx-out flag that is malformed, as it is missing any value.

This problem has been temporarily solved within the sam/testrun branch, here
We'd like this solution cleaned up. (see the other issues for the other changes there)