-e: see title, starts in 2018.2.0a5
--workaround: disable stripping engine code

-repro:
--create new project or open attached one
--build&run for WebGL
--NOTICE scene stays black and an error is being logged:
---Could not produce class with ID 150.
---This could be caused by a class being stripped from the build even though it is needed. Try disabling 'Strip Engine Code' in Player Settings.

-150 is PreloadData (see https://docs.unity3d.com/Manual/ClassIDReference.html)