Crash when providing `-signer` instead of `--signer`

[joshuahannan]

Problem

When running a transaction with flow transactions send, if you provide -signer instead of --signer, then the cli crashes with no helpful error message and a confusing stack trace.

Steps to Reproduce

Run any transaction, but only use one dash for -signer instead of two.

Acceptance Criteria

Clear error message about what is going wrong

Context

Not blocking anything