Join/Left event error in Console

Hi,
I just wanted to program a PLAYERJoin / QuitEvent ..
In my opinion everything is correct, but I get the following error in the console:

https://hastebin.com/toqesefewi.cs

Here is my code:

https://hastebin.com/lunodetuco.java

I do not know what the mistake is ...
I also registered the event as normal in the Main.

Does anybody have a solution?

 

Can you post your config file?
Edit: you have to put a path for getting a string from a config file
Example:

Code:

Example: "String Example"

getconfig().getString("Example")

 

Also there is no point to calling e.getJoinMessage(); or e.getQuitMessage(); if you don't plan to do something with the result. You should not be embedding the color character either, the ChatColor enum exists for a reason. You especially should not be using color codes in as config paths.