The penguin doesn't have a loot table. Shouldn't it be empty rather than null?

Well maybe. Is it causing some sort of issue because it is null?

It means that penguins can not have their drops modified by mods that edit the loot table. I am also working on a mod that uses the loot table data so this would cause incompatibilities there.

I guess yea. Only really thought of a way of modpack makers to modify the penguin drops (Can just enable the fish dropping, and then alter that loot table).
Will just add a empty loot table by default I guess :)