Project Settings -> Engine -> Collision : Scrollbar initially missing

If the Project Settings window is sized to the point a scrollbar is needed to read the complete text for Collisions Settings, expanding "Preset" will result in the scrollbar not appearing initially, until the "Preset" option is closed and expanded again.

REGRESSION: *Note: User described this as an "age-old" issue but I was not able to repro this in UE4.11 or UE4.10 after I successfully repro'd this in UE4.12.

1. Open any project
2. Edit -> Project Settings -> Engine -> Collision
3. While the window is smaller than required, expand "Preset", it will fall off the screen and no scroll bar will appear
4. Re-collapse then expand "Preset" once again and the scrollbar appears.

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Project Settings -> Engine -> Collision : Scrollbar initially missing