Make sure you've done the following:

• You're using the latest build for your server version
• This isn't an issue caused by another plugin
• You've checked for duplicate issues
• You didn't use /reload

Dump : https://pastebin.com/4v4UeX24

Description :
Every time a player join the server, we get this stacktrace : https://pastebin.com/Te9pkDLq
Do you know from where it comes and if you can fix this ?

Thanks !

Fixed with an update.