Called to get the Mod ID of the mod that created the ItemStack, instead ofthe real Mod ID that registered it.

Returns:the Mod ID for the ItemStack, or null when there is no specially associated mod and IForgeRegistryEntry.getRegistryName() would return null.

according to the forge's comments, all these implementations should return the mod id, instead of a Component.

related issue: Snownee/Jade#102