Is that the only actual error? Or is the null reference one a warning? Seems like the dark optimizer runs at avatar build time, and it’s unhappy with something. Maybe check the root of the avatar for an animator component? I know the VRChat SDK itself has issues complaining about a missing animator.
Maybe the dark optimizer has a warning message saying something?
Good SDK feature here. If it didn’t abort, you’d risk your avatar being replaced with unusable garbage data. Also good indicator of where to stop reading messages