So a bunch of friends and I were trying to play on a LAN server, one computer, the beefiest of us all was hosting, and the rest of us were going to connect. Everything was great until we tried to connect to his PC. When doing so we would get "Internal Exception: Java.lang.IllegalArgumentException: Itemstack ingredients cannot be created using the empty ingredient.".

I don't have the logs but ran the game with the active output log option from the Minecraft launcher, tried to join the world again, and figured out it was Mekanism throwing the error. Upon removing Mekanism, as well as all its dependencies, the issue was fixed and we were able to play, no issues.

I don't know if this issue is on your end or Mekanisms but I thought I'd post here so you guys would have the information, or maybe you could shed some more light on the subject for me.

If any more information is needed please let me know.

Modpack Version:
0.2.51

Steps to reproduce:
1.) On one Pc open a singleplayer world
2.) open that world to LAN
3.) On another computer attempt to join that world
4.) error

latest.log

had something before... it's just some mod that checks out for internet connection. find mod called logprot and remove it from all members, doesnt affect on gameplay. Text me if it doesn't help

I tried removing logprot on everything and it didn’t work, reverted the change, then looked at the log output. Found mekanism was throwing the error, removed it along with its dependencies and it fixed the issue.