broacast on an empty [chain]/[key] outputs the wrong error message

Tried to broadcast a tx but the path is empty on S3, instead of error saying files are not there, got a message saying needed signatures. It would make more sense show the right reason why it failed to broadcast (no files).

Got this error:
```
$ multisig broadcast cosmos ceph-cosmos
Error: Insufficient signatures for broadcast. Requires 2, got 0
```

But reason is fails is this:
```
$ multisig raw cat cosmos ceph-cosmos
No files in cosmos/ceph-cosmos
```