Same user name showing up many time in the Assignee suggestion list in case that the user name got "\"

Here is the steps to reproduce the issue:

1. Create a new user with the user name like "test\123456".
2. Assigne one issue to this user.
3. Re assigne the same issue to other user.
4. Assigne the issue back to the same user, then we can observe that the same user name "test\123456" display many time in the suggestion list.

Impact: the suggestion list will increase with the same user name on each search request, and the web browser will finally hang as it run into 100% CPU.

Workaround solution:

1. Remove the slash in the user name.
2. Upgrade to JIRA 5.2.