`FabricDefaultAttributeRegistry` states it throws an exception when provided with a non-null value

<img width="910" height="97" alt="Image" src="https://github.com/user-attachments/assets/8c919061-51ee-44a9-bd5b-a340c251a25d" />

https://github.com/FabricMC/fabric/blob/ce6f2470059ba08c53f75e1ebdc28004c9bf1063/fabric-object-builder-api-v1/src/main/java/net/fabricmc/fabric/api/object/builder/v1/entity/FabricDefaultAttributeRegistry.java#L80-L85