The bug happened when I used /essentialcommands rules, then I was kicked out of the server.

The error message:

And this is my rules.txt:

啊什么？你还想开挂？
------------服务器规则------------
1. 不要开挂
2. 注意你的言行
3. 不要人身攻击
-----------------------------------

It's in Chinese, I don't know if this is the reason for the error.