Light function materials using WorldPosition do not render correctly to volumetric fog if there is more than one

There is a one-line fix for this in a shader file, see their PR on GitHub:
https://github.com/EpicGames/UnrealEngine/pull/10251/files

1. Download the licensee repo from
https://udn.unrealengine.com/s/contentdocument/0694z00000PlT1BAAV, open project
2. Observe the two spotlight setups. They should be identical, white, but with some color
in them. One instead will be colored