I get this only when trying to run a modded server (client runs fine). I don't know anything about java and unfortunately don't have time to learn atm, so I would really appreciate your help.
Crash report: https://pastebin.com/VERT4xEB
If you want to try to reproduce the issue, I've uploaded my mods to: https://drive.google.com/open?id=18nnOBJ83Ntjc616aU_iySo3gJ3OIj2R1
Remove mods one by one till you find the culprit.
I got it to work, forestry was crashing the server unfortunately.