Add People option is case sensitive when search is disabled

If we enter an email address that is assigned to a user on ‘Add people to this request’ pop-up, but at least one of the letters is in lowercase when it should be in uppercase (or vice versa), Service Desk does show the user (which means that the user is found) but it hangs and don’t add the user as a participant. See screenshots for more details.

We can confirm that Service Desk is able to find the user because if we set ‘Customers can search for other customers when adding participants’ option to ON, it is possible to find users even if we enter their name/email using the wrong case.

Noticed on Cloud instances - JIRA Service Desk v2.3-OD-08-002-D20150218T054701