[1.6.4] TransferStackInSlot doubling my items

[andreidim]

Hello everyone, while working on my mod I tried to make a chest, I followed the containers and GUIs tutorial from the wiki, it works, but, there is a small problem, when I try to transfer my items by doing shift+click, when transfering stuff from the tile entity to my inventory, the items get doubled, here is the code for the transferStackInSlot function: https://gist.github.com/anonymous/5c4df7bcc699c46c12ae