If a user has no domains selected they're denied access to all sites. It's pretty standard when limiting access to thing through a checkbox field that none selected means no restrictions. This is how it works when assigning other entities to domains. This is an issue for sites that are installing this module in an active site if they have a large established userbase.
Install the module, try to login as a user that has no affiliated domains set.
Make default behavior if the user has no domain affiliation set that they have access to all domains.
Would a patch that accomplishes this be accepted or is this behavior intentional for some reason?
Closed: won't fix
1.2
Code
I spoke too soon. After considering use cases the way it currently works makes the most sense considering the affiliated domains for a user account isn't necessarily meant as a restriction, more a way to identify their affiliation so restricted content later can make decisions.
This can be closed.