When editing a course's groups (group/index.php), the breadcrumb navigation is missing some information if you navigate back to it from the add/remove users interface (groups/members.php)

Steps to reproduce:

1. Log in as admin to a moodle website, make sure it has at least one group
2. Navigate to Admin/Users/Groups (the groups/index.php page)
3. The breadcrumb should display as Course/Users/Groups
4. Select a group and click the 'Add/Remove Users' button
5. Click the 'Back to Groups' button
6. The breadcrumb now shows 'Course' only, which is incorrect
7. The breadcrumb should show Course/Users/Groups, just like the first time index.php was accessed