[1.21] Fix empty slots having a slot limit of 1 in ItemStackHandler.

[MerchantPug]

By using ItemStack#getMaxStackSize, you are limiting any empty slot to have a slot limit of 1, as that defaults to 1 when there is no max stack size component present (empty stacks don't have it).

The fix is to instead getOrDefault the stack size component and default it to max value, that way, mods that increase the max stack size further than 99 can also be slotted into empty slots.

[IThundxr]

I'm not entirely sure setting it to int max value is the best fix here, previously ItemStack#EMPTY had a stacksize of 64 so ideally it'd default to the default stack size

[MerchantPug]

I'm not entirely sure setting it to int max value is the best fix here, previously ItemStack#EMPTY had a stacksize of 64 so ideally it'd default to the default stack size

That's fair, I'll change it then.

[MerchantPug]

accident!