Fixing bug which causes WebGL warning: "RENDER WARNING: Render count or primcount is 0"

[adamblok]

I noticed that for some models the library produces WebGL tons of warning:

RENDER WARNING: Render count or primcount is 0

After debugging I discovered that it's related to the transparent rendering mode. I don't know the exact reason of this bug, but it looks like it occurs when we load a model which doesn't have any transparent objects.

Fortunately the fix was quite simple and safe :).

You can get the models that produce this warning below, so you can reproduce it in your environment: models.zip

[martin1cerny]

This has already been fixed in develop branch.