* ignore `instance.actor` when checking if there are local users
We've seen this happen a few times:
* there was some AP software at $some_domain
* it gets replaced by Misskey
* before the first user can be created, an AP activity comes in
* Misskey resolves the activity
* to do this, it creates the `instance.actor` to sign its request
* now there *is* a local user, so the `meta` endpoint returns
`requireSetup:false`
* the admin is very confused
This commit factors out the check, and doesn't count the
`instance.actor` as a real user.
* autogen bits
bafef1f8b4