When creating REST connection profile there is couple of issues with security settings:
1.) When user changes security settings to HTTP basic and doesn't enter any credentials Wizard shows error, but user is able to finish the creation without problems
2.) When user changes security settings to HTTP basic and then they want to change it back to 'none', wizard complains that there is no username entered and won't let you finish the creation of the connection profile.
See video in comments (too big for JIRA)