Getting value at index as an item stack always returns "0 air"

[OllyTPK]

I do hope I'm just doing something wrong here but when retrieving any value within a list as an ItemStack it will always return as "0 air" on Array Lists - 2.4.7. I've searched the internet for any indications but can't find anything promising or has worked. I've recreated your video on retrieving ItemStacks tested that and now modified for debugging yet still no changes. Any help would be appreciated.