Hand showing up twice when switching from a tool to a blank slot

Idk if this is a bug or not, if its not. Oh well. (For example) your holding a lead and switch to a air block (or whatever no items called) your hand shows up once when your holding it and twice when you put it away and you show your hand. It doesnt do the same to wood or any other blick though, if you compare the 2 theres a difference between putting a tool away and a block away.... if you see it in slow motion its very obviouse.