geckolib problem with texture change

Hello, I generally need some help. I have a problem with GeckoLib. I’m using MCreator 2024.4 and working with GeckoLib.

I created a mob as an animated entity, and I wanted it to become invisible when it gets hit. It turned out that invisibility doesn’t work on custom models (at least that’s what it seems to me).

So I wanted to change the mob’s texture to one where only the eyes are visible. I created a procedure:
Entity is attacked
which detects if the mob hits the player. If so, it triggers:
if entity element (mob name) is the source entity then set texture to (texture name)

But unfortunately, this crashes the game. Any ideas on how to fix it? ;-;