(Forge 1.12.2)
The game always crashes when I use any shader near the helicopter mob. The singleplayer world shutdowns and gives me this error:

The game crashed whilst rendering entity in world
Error: java.lang.ArrayIndexOutOfBoundsException: 5

I tried with a different optifine version but it still crashes. Without any shader it works fine and
with any other mob it has no problems as well.

#131, #139

this should be fixed already in 2.0.2.0_pre3.2, which version do you use?