I was playing normally until I closed my server to stop playing because one of my friends played on the server but did not want to turn on because the quark launched an error, I will leave the version which use to try to solve the problem and the crash report of the same where it indicates everything.

Previous version: Quark-r1.6-179.jar
Version Minecraft: 1.12.2
Version Server: Magma 1.12.2 (vc3242d9)
New trial version in case of error: Quark-r1.6-178.jar
Version of AutoRegLib: AutoRegLib-1.3-32.jar
Crash report: https://gist.github.com/xlCyanz/7189b06dfa589d1d4f30f72753595b07

Not sure why this is happening, but you can sort it out by disabling the better flower pot feature.