Error message.startsWith is not a function

Hello, I wanted my bot on command !joke from my database did not get an anecdote, but it gives an error: message.startsWith is not a function

const tmi = require('tmi.js')
const mysql = require('mysql')

const conn = mysql.createConnection({
    host: "localhost", 
    user: "twitch",
    database: "joke",
    password: "pass"
})
conn.connect(function (err) {
    if (err) {
        return console.error("Error: " + err.message)
    }
    else {
        console.log("Connect MySQL")
    }
})

let query="SELECT * FROM joke"

conn.query(query, (err, result, field) =>{
    console.log(err)
    let arr = result
    let rand = Math.floor(Math.random() * arr.length)

    const client = new tmi.Client({
        options: { debug: true },
        connection: {
            reconnect: true,
            secure: true
        },
        identity: {
            username: 'streamcommunebot',
            password: ' ...  '
        },
        channels: ['dummo']
    })
    client.connect()
    client.on('message', (channel, tags, message) => {
        if(message.toLowerCase() === '!joke') {
            client.say(channel, rand)
        }
    })
})

conn.end( err => {
    if (err) {
        console.log(err)
        return err
    }
    else {
        console.log('Database ----- Close')
    }
})

tmijs / tmi.js

Error message.startsWith is not a function #391