Forge: An exception thrown during transformation should show the transformer as failed
Forge transformer: remove unnecessary mappings check (it's never null now)
Forge ASM: Don't bother looking at any org.getlwc.asm classes while transforming. This fixes PistonUpdateStateTransformer.

When AbstractMultiClassTransformer is first loaded and transform is called on the class it needs, Forge decides to tell all transformers about AbstractMultiClassTransformer, so the piston transformer then gets called transform(AbstractMultiClassTransformer)