I am creating a custom mod pack and am having a client crash due to the error in the crash report. I am reporting here first, but I don't know if it is a Croptopia, Patchouli, or Quark error.
It has occurred two to three times opening a chest and once opening the creative menu.
Crash report: https://gist.github.com/kezmodius/f28f616b8f4093aaad9963324dc07271
Latest log: https://gist.github.com/kezmodius/68f0c0ecdf41feeb4e83964e54ac141f

I did some more testing on this issue and it does not crash the game in single player. However, if I try to open the Croptopia guide this is the message I get.

Sorry, user error. Apparently my server decided Croptopia was client only and did not install it. Installing it on the server fixed the issue (of course!)