a friend was hosting a lan world and i kept crashing trying to look up various recipes,
Crash Report : http://pastebin.com/Pspud8VB
Can someone please at least help me understand what caused it?
also, how do i tag this as a bug?

This is a consequence of #411. Mutations are not synced from the server to the client if you are connecting to a lan world, resulting in this crash.
And you can't tag issues, but I can.