Project administrator cannot edit Project Lead/Default assignee if they are not granted the Jira Admin global permission

Summary

A user who is a member of the Project Role (Administrators) which has been added to the Administer Project permission is unable to edit the Project Lead/Default assignee, if this user is not grated the Jira Administrators global permission.

According to the documentation, the Administer Project permission allows any user w/ the permission to edit the Project Lead:

Permission to administer a project in JIRA. This includes the ability to edit project role membership, project components, project versions and some project details ('Project Name', 'URL', 'Project Lead', 'Project Description').

However, with this bug, a user with the Administer Project permission is unable to edit the Project Lead. No errors appear in the UI or in the logs.

Steps to Reproduce

1. Log into Jira as a user who has Jira Administrators global permission
2. Go to the user management page, and create a user (referred to as "testuser")
   1. Grant this user Jira application access
   2. Do not grant this user with the Jira Administrators global permission
3. Create a new project
4. Go to the page Project settings > Users and Roles
5. Grant the user "testuser" the project role Administrators
6. Click on the Edit defaults button and try to set any user as the project lead
7. Verify that this user is properly added to the "Project Lead" field
   
8. Log into Jira the user "testuser" and navigate to Project settings > Users and Roles
9. Click on Edit Defaults
10. Change project lead to another user and click on Update
    

Expected Results

The update completes and pop-up window closes. User is able to update changes to Project Lead and you see the Project Lead correctly updated on the page:

Actual Results

Instead, the following happens:

• The project lead does not change and a blank picture is displayed next to it:
  
• When the page is refreshed, the lead project shows the original user:
  

Workaround

Grant the user who is unable to edit the project lead with the Jira Administrators global permission. If you grant the user user with this global permission, they will be able to edit the Project Lead.
Or if that is not possible, another project administrator who has the Jira Administrators global permission can make the change.