Issue Summary

Very minor UI bug.  Newly added user renders double row on Default Reviewers pane.  See attached screenshot.

Steps to Reproduce

1. visit repo settings
2. visit "Default Reviewers" pane
3. enter user name so that autocomplete finds the user
4. add user (use "enter" keyboard key or "Add" button, does not matter")
5. user renders double row

Expected Results

Newly added user renders once.  As it is now, it confused the user (me!) into deleting the redundant row, which deleted both rows, making me re-enter the just-added user, realizing it's a UI bug rather than user error ("did I accidentally double-click the 'Add' button?")

Actual Results

The below exception is thrown in the xxxxxxx.log file:

...

Workaround

User (me) realizes there's a UI bug and proceeds as if the user is not doubly-rendered.