Set username to be email address

Hi,

I'm working on a site for a client, they have purchased the Professional version of Community Builder, and I'm trying to get the username to be populated with the user's email address. In CB > Configuration > General I've set the Login Method to Email Address, and in CB > Field Management I've made the username field not required. I've then used CB Auto Actions to create an action to set the Username field to

I finally figured out what was wrong, the site had an entry in the users table with an empty username - no idea how that had happened!