No scroll bar is created when the Collision Preset section of Project Settings is expanded

No scroll bar is created when the Collision Preset section of Project Settings is expanded. Clicking an element in the Preset section does not add the scroll bar.

Collapsing the section and re-expanding it creates a scroll bar, as does resizing the window.

Reproduced in 4.7.2 binary and Main (//depot/UE4/Promotable-CL-2478413)

1. Open any project
2. Edit > Project Settings > Collision
3. Expand the Preset section

Result:
No scroll bar is created. Clicking an element in the Preset section does not add the scroll bar.