#19 Duplicate users can be created without issue

[Zeke Gilbert]

1) Log in as admin
2) Navigate to Adminstration
3) Create a new "tester"
4) On the refreshed page, using the same name, create a duplicate user

Expected results:
An error message should be seen, stating that the username is taken, and the user is not added

Actual results:
Duplicate user is added. Also, through this process, blank usernames are allowed.