Fix multiple enrolled alert.
*Merge deadline*: "None"
1. Run [edx master devstack](https://github.com/edx/devstack).
2. Run [frontend-app-learning](https://github.com/edx/frontend-app-learning).
3. Visit http://localhost:18000 and login as staff.
4. Visit http://localhost:2000/course/course-v1:edX+DemoX+Demo_Course/outline.
5. Click on `Introduction` section and then `Demo Course Overview` link.
6. You should see only a single alert.
7. Press the back button of your browser.
8. Again perform `step 5`.
9. You should see only a single alert. If you see more than one, the issue is not fixed otherwise fixed.
*Author notes and concerns*:
1. I am using [lodash](https://lodash.com/) library which is already being used by this project's 129 dependencies.
[ ] @xitij2000