Script Context.CoreScripts/AvatarMood:251: attempt to index nil with 'FindFirstChild'

I am writing a complicated system to allow the player to change their character, without resetting the humanoid or GUI, but I am getting this core script error. Anyone know why?

Script Context.CoreScripts/AvatarMood:251: attempt to index nil with 'FindFirstChild' 

I’m getting the same issue. It only happens when my original Avatar is using the new facial animations. It doesn’t seem to cause any issues but I’m getting a bunch of error logs because of it.