Scroll ability lost after drawer collapse

On a reduced viewport when the drawer is now triggered to view on top of the main screen, dismissing the drawer either by clicking the greyed out area OR clicking the close results in the drawer results in the page scrolls being disabled and only re-enabled if refreshed.

Tested on local and QA

With QA:

1. Open a browser with a reduced width (900x950 should work)
2. Log into the QA site as a teacher/admin
3. Go to the course 'Activity Examples'
4. Confirm you see the scrollbar and can utilise it
5. Click on the 'Open block drawer' icon
6. Close the drawer either via the close icon OR clicking on the greyed portion of the course page
7. Note the scroll bar has now vanished and you cannot scroll

Expected - page scroll bar should exist when the drawer is disabled.