Thanks for sharing. You may be on to something. THE HUMAN IS BACK!!!
This might be at least some clue to tracing down this specific issue. We'll take a look at this in some other environments and see if we can glean anything.
I will note that commenting out these lines ** DID ** CAUSE THE HUMAN to start displaying on MacOSX MOJAVE as well (The first time didn't work because I forgot to include commenting out the shader.py lines which were the difference). Now we need to study why.
As an additional testing comment, after getting the human back, I tried Rendering;\ | Scene and cold lights or Render | Scene warm lights .
They seemed to work when the human had the default "generic skin", but they produce an error if a regular skin texture is applied first, so I'm not sure what the status is with respect to any shader activity following the "commenting out." This maneuver effectively makes the human "disappear again" and get replaced by a white panel. The only way to get the human back is to restart.
BTW, the splash screen is missing the "image" when running on macOSX from source.