Description of problem:
A non-name user can be created. 

Version-Release number of selected component (if applicable):
0.96

How reproducible:
Every time

Steps to Reproduce:
1.Click "default" hardware pool.
2.Click "User Access" tab.
3.Click "Add user" button
4.Select one role in popped dialog and click "Create User Permission“ button.
5.Click "Add user" button
6.Select one role in popped dialog and click "Create User Permission“ button.
7.Click "Add user" button
8.Select one role in popped dialog and click "Create User Permission“ button.
  
Actual results:
After step5,a null user name is listed in the list.
After step6,a non-name user has been created.
After step8,it prompt "Error Adding User:Validation failed:Uid has already been taken".


Expected results:
The null id can not be used.
User can specify user name or provide an interface for users to specify other members.

Additional info: