bug: invite code stuck

Commit: cdbbaaccdf85093c50797281f3e08b6f4f90901b

I have an invite code stuck in the Available state, but it cannot actually be used to register a new account.

I'm not sure how I caused that, so I don't have any reproduction steps.

In the database it seems to have -1 available_uses, while also not having an entry in the invite_code_uses table.

Please let me know if there's anything I can provide to assist debugging!