"Required" setting doesn't work if "user role title" is left blank

if using "user role assignment", and "required" is checked, and the user does not select a role, they are assigned a role at random (or perhaps it's the last role listed? or the first?)

the form should have some validation and return an error if role is "required" but the user does not select a role.

alternately, or additionally, it should be possible for the admin to choose a default, and for that default to be "checked" when the registration form is displayed to the user.