Minecraft version & Mod Version:
1.20.1, 1.3.1

Single player or Server:
Both

Describe problem (what you were doing / what happened):

You shouldn't return null for an Ingredient. Use Ingredient.EMPTY instead. Otherwise it is possible to catch NPE from mods which are trying to get that value (Even IntelliJ says the Ingredient value will never be null, but your code proves its wrong :)