Assignee picker shows last user twice

Summary

The assignee picker can show duplicated last user on the list, compounding on multiple clicks of the assignee field.

Steps to Reproduce

1. Create a Jira instance with 15 or more users
2. Create a project with an issue in it, and assign the issue to one of the users
3. Change the assignee to another user, and refresh the issue
4. Click the assignee field, and scroll down the list

Expected Results

No users are duplicated.

Actual Results

Last user on the list will be duplicated in the list.

Notes

There are multiple requests to the <base-url>/rest/api/latest/user/assignable endpoint. The rest endpoint is hit when clicking the "down" arrow, and when scrolling to the bottom of the list.

Workaround

There is no workaround at this time.