Fix panic from waypoint hostname delete with no hostname specified

[gulducat]

A lil order-of-operations issue resulted in an unsightly panic.

Before:

❯ waypoint hostname delete

panic: runtime error: index out of range [0] with length 0

goroutine 1 [running]:
... trace ...

After:

❯ ./waypoint hostname delete
! hostname required for deletion

[hashicorp-cla]

All committers have signed the CLA.

[briancain]

thanks for the fix! It seems like heroku build packs are a bit broken at the moment, so that's why the integration tests are failing. Otherwise if you sign the CLA we'll be good to merge! 😄

[gulducat]

sure thing! I did a force-push to update my author email for cla-assistant (which I'm partially responsible for operating, so really should have known to do that before making a PR 😋)