Quickbar: Fixed creating a new stack pushing others off the quickbar

Picking up a block while not having a partial stack of it (a multiple of 64 or 0 of the item) was pushing all the other quickbar items down one (so, one disappears), this fixes that.

fogleman seems to want to keep his build simple and small, and it seems this repo is the main one gathering third party work, so I figured I'd submit here.

Is there an IRC or something we could discuss this project in? irc://irc.gamesurge.net/Pinecraft perhaps?