Assignee not changed when moving issues between projects with different permission schemes

Summary

• In v6.3.15, when moving an issue to a different project where the logged in user does not have "Assign Issues" permission the user is automatically assigned to the default for the new project
• Doing the same after the upgrade in 6.4.11, the moved issue still have the original asignee although he is not an "Assignable User" in the new project.

Environment

• JIRA 6.4.11

Steps to Reproduce

1. Create 2 Projects with 2 separate permission schemes ( Project A & B )
2. Create 2 users User A and User B
3. In the permission schemes for Project B, make sure that User A is not given the "Assignable User" permission
4. Confirm this by trying to assign an Issue from Project B to User A. User A must not be able to be the assignee of that issue.
5. Create an issue from Project A , Assign it to User A.
6. Move the issue to Project B
7. Take note that the assignee of the issue did not change. It is still User A who does not have the "Assignable User" permission in Project B.

Expected Results

1. Assignee of moved ticket is automatically assigned to the Default Assignee for the new project

Actual Results

1. The assignee of the issue did not change. It is still User A who does not have the "Assignable User" permission in Project B.