Fix NPE when FoodProperties is null

[Huoyuuu]

ModConfig.getFoodConfig can crash with NPE when SOLValheim.getter.get(stack) returns null and we call food.getNutrition().

var food = item == Items.CAKE
        ? new FoodProperties.Builder().nutrition(10).saturationMod(0.7f).build()
        : SOLValheim.getter.get(stack);
// ...
existing.nutrition = food.getNutrition();

This PR adds a null guard if (!isDrink && food == null) return null; to skip autogen for such items and avoid client crashes (e.g. tooltip/UI).