[unsolved] Need help with items !

I need to detect items in an item slot, but the items return null if i use a check in my renderer file !

the idea : have an inventory that opens with a key command, enter an item in a slot, and let the entity change model depending on the item.

The only problem is, as Renderer's are client side, it wont read my code ! Because it gets saved client side

http://paste.ubuntu.com/1683515/

here's a paste of how i save the code in my container and inventory.

the data has to be player specifique.

thanks for reading, and a like if you answered/helped me !