On View issue page, when trying to change the status of an issue to assigned and the issue is already assigned to a user who is no longer authorized to handle issues (e.g. former developer downgraded to reporter), bug_change_status_page.php throws an Access Denied error.

This is not consistent with how such situation is handled for any other status (e.g. it is possible to change it to resolved without error) and in other situations (e.g. from bug_update_page.php).

We should only throw the error when the page's handler_id parameter is different from the issue's current handler.