Discovered by meowmiomew while testing MDLQA-18513.

After adding the navigation block to the dashboard and expanding one of the course sections using the keyboard, all activities are shown duplicated

Steps to reproduce

1. Add a navigation Block on the dashboard (for boost site admin -> appearance ->themes -> boost settings icon -> remove the navigation the unneeded blocks setting)
2. Navigate the navigation block using the keyboard
3. Expand a course and then one of the sections of that course.
4. Verify all activities are duplicated