beet config with empty configuration could show a message

[Sudo-kun]

I'm new to the project so maybe I just forgot to do something.

I was just looking around and found that when calling config while nothing was configured showed an empty array.

Maybe there could be a text that says "No existing configuration".

[sampsyo]

Sure, sounds good. But I'd phrase it as "empty configuration" instead of "no configuration" because the symptom would be the same if there is just an empty file there.

[jackwilsdon]

Fixed by #3782.