can accept calls during setup wizard, but can't hang up

While the setup wizard is active, incoming calls can be accepted but the dialer app isn't displayed. This lets the user talk, but they can't mute or use the speaker or press numbers or, most importantly, hang up.

I saw this a few images ago by accident, but just re-confirmed it on Utopic 166.

I doubt this is a high priority at all since the user only sees the welcome wizard once (or once per flash/wipe, a developer-only operation), but it'd still be nice if we could show the dialer.