Multiple 'messages' in a YAML file

Hello, I have followed this tutorial by Reflxction https://bukkit.org/threads/creating-and-managing-custom-yaml-files.473063/ to create a YAML File with a message in it that is outputted to the user when they join the server. However, I have made a second message for when the user leaves the server, but this breaks both the join and leave messages. I copy and pasted the code within the listeners class, but replaced every 'join' with the word 'quit' and added my message to the YML file. I am unsure as to why it is breaking both of the messages.
NOTE: I have not changed anything within my main plugin class in order to add the quit message and I am fairly sure that shouldn't be a problem as my Listeners class is the only one that mentions separate messages.

My YML File:

Code:

Messages:
  OnJoin: "&eWelcome to my Kingdom!"
  OnQuit: "&eWe will miss you!"

My Listeners Class:

Code:

package me.Piggo564.YML;

import org.bukkit.ChatColor;
import org.bukkit.event.EventHandler;
import org.bukkit.event.Listener;
import org.bukkit.event.player.PlayerJoinEvent;
import org.bukkit.event.player.PlayerQuitEvent;

public class Listeners implements Listener {
  
    private App app;
  
    public Listeners(App app) {
        this.app = app;
    }
  
    @EventHandler
    public void onPlayerJoin(PlayerJoinEvent event) {
        String unformattedMessage = app.getMessagesConfig().getString("Messages.OnJoin");
      
        String formattedMessage = ChatColor.translateAlternateColorCodes('&', unformattedMessage);
        event.getPlayer().sendMessage(formattedMessage);
    }
  
    @EventHandler
    public void onPlayerQuit(PlayerQuitEvent event) {
        String unformattedMessage = app.getMessagesConfig().getString("Messages.OnQuit");
      
        String formattedMessage = ChatColor.translateAlternateColorCodes('&', unformattedMessage);
        event.getPlayer().sendMessage(formattedMessage);
    }

}

 

When you say "it breaks", what do you mean? Does it throw an error? What is the error? Also getString is nullable, so you should be checking for that.