Users part of Group name starting with Turkish character are not recognised as assignee

Issue Summary

This is reproducible on Data Center: yes

Users part of Group name starting with Turkish character are not recognised as assignee even when the Group has necessary Project permissions.

Steps to Reproduce

1. Create a Group starting with Turkish character, for eg- "İstanbul" and assigned few users to this group as below:
   
2. Give "İstanbul" group, "Browse Project" and "Assignable User" Permission.  Also, ensure, the user with which you are logged in and you want to assign an issue to users from group "İstanbul" group also has "Browse Project" and "Assign Issue" permission. 
   
3. When you try to select any users from the group "İstanbul" as assignee, the users from this group are not searchable as assignee.
   

However, when the same users are part of a Group with English character, for eg- "New Group" and , then the users are search

Expected Results

Users part of Group name starting with Turkish character should be recognised as assignee when the Group has necessary Project permissions.

Actual Results

Users part of Group name starting with Turkish character are not recognised as assignee even when the Group has necessary Project permissions.

Workaround

Use group name with English characters.