onions/detached and onions/current should return empty lists instead of errors
If you do a GETINFO query on onions/detached or onions/current and there aren't any, a 551 error is returned. Most other things just return an empty list/value in this case and I think these should too.
One consequence of this is that if you ask for onions/current with some other keys and there are no current onions, the whole query will fail.
So GETINFO onions/current should return onions/current= instead of an error.
For example you can try carml cmd getinfo orconn-status onions/current to see this behavior.
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