## Issue
Closes 5721: Publish-Preview updates
## Changes
(1) Match the recent "incognito" change that sets the channel to `undefined` via `updatePublishForm`. This change would also cover `null` -- I don't think it's being used to represent something else, so showing "Anonymous" for `null` should be fine.
(2) Added channel icons, so it'll be more obvious to the user if they accidentally selected the wrong channel.