Missing "-none-" audience when creating group content

Situation:

1. 'Project' is a content type that is defined as group content.
2. The 'authenticated' user role has (core-level) permissions to create 'project' content on the site.
3. User 'lonewolf' is an authenticated user and not a member of any group.
4. User 'socialite' is an authenticated user and member of one or more groups and has permissions to create group content.

When 'lonewolf' attempts to add a 'project' node, the audiences selection box gives him a single option: "- None -". This is fine and as expected, since he has no permissions for any groups.

When 'socialite' attempts to add a 'project' node, the audiences selection box gives him a list of groups for which he has permissions. HOWEVER, there is no "- None -" selector.

This means that if he inadvertently clicks one of the groups, he can not undo the selection without refreshing the entire screen, and losing all his entries.

I have seen online videos where the audience selector first shows "- None -", then lists the available groups, which is what I'm after.

Can anyone tell me what I've misconfigured?