错误-（节点：8240）UnhandledPromiseRejectionWarning：ReferenceError：未定义ling

Question

并且在测试机器人时出现错误，请帮助我修复它。我试图在Internet上找到一种解决方案，但是有完全不同的错误:( 我将感谢能帮助我的人！这是代码。

const Discord = require('discord.js');
const bot = new Discord.Client();
bot.commands = new Discord.Collection();
const fs = require('fs');
let config = require('./botconfig.json');
let token = config.token;
let prefix = config.prefix;

fs.readdir('./cmds/',(err,files)=>{
    if(err) console.log(err);
    let jsfiles = files.filter(f => f.split(".").pop()=== "js");
    if(jsfiles.length <=0) console.log ("Такой команды нет!");
    console.log (`Загружено ${jsfiles.length} команда`);
    jsfiles.forEach((f,i)=>{
        let props = require (`./cmds/${f}`);
        console.log (`${i+1}.${f} Загружен!`);
        bot.commands.set(props.help.name,props);
    })
})

bot.on('ready', () => {
  console.log (`Запустился бот ${bot.user.username}`)
  bot.generateInvite(["ADMINISTRATOR"]).then(link =>{
      console.log(ling);
  })
});

bot.on('message', async message => {
  if (message.author.bot) return;
  if (message.author.type == "dm") return;
  let user = message.author.username;
  let userid = message.author.id;
  let messageArray = message.content.split("");
  let commands = messageArray[0].ToLowerCase()
  let args = messageArray.splice (1);
  if (!message.content.startstWith(prefix)) return;
  let cmd = bot.commands.get(command.slice(prefix.length));
  if(cmd) cmd.run(bot,message,args);
  });

bot.login(token);