Unable to select object when using DistanceToNearestSurface node for Opacity Mask in Masked Material

From observations, this seems to be related to how the mesh selection works, and may be
making the pixel under the mouse masked away. Adding a value >= 0.5 between the clamp
and the Opacity Mask output in the material allows it to be selected again, so it's not just the
presence of the DistanceToNearestSurface, but how selection will pass through objects with
masked materials’ transparent areas.

1. Download licensee repro - https://udn.unrealengine.com/s/contentdocument/0694z00000PibeZAAR
2. Try and select the green cube (It won’t work)
3. Edit the material on the green cube, detaching the output pin for Opacity Mask
4. Apply, try and select green cube again (It will work)