Translucent Water renders dark with Lumen enabled.

Regression tested in 5.1 at CL 23901901 where the issue still occurs.
The material will still have the normal and reflective properties.

1. Open any project
2. Enable the Water plugin
3. Enable "Support Hardware Raytracing" in project settings
4. Restart the Editor
5. Open a basic level
6. Place a plane into the world above the floor mesh
7. apply MI_Pool_01 to the plane
8. Add a Post Process Volume to the level that encompasses the plane and the camera
9. In the settings for the PPV, Enable Lumen and set translucency type to raytraced
   Actual Result:
   The water will render black and will loose all transparency.
   Expected Result:
   The water continues rendering blue and will be transparent.