Electron ignores setThumbarButtons([])

I just started to learn about electron. I want to create a window without the Thumbar Buttons, but electron ignores the .setThumbarButtons call
This is my main.js from a tutorial:

const electron = require('electron')
// Module to control application life.
const app = electron.app
// Module to create native browser window.
const BrowserWindow = electron.BrowserWindow

const path = require('path')
const url = require('url')

let mainWindow

function createWindow () {
 
  mainWindow = new BrowserWindow({width: 800, height: 600})
  mainWindow.setThumbarButtons([])

  mainWindow.loadURL(url.format({
    pathname: path.join(__dirname, 'index.html'),
    protocol: 'file:',
    slashes: true
  }))


 
app.on('activate', function () {
 
  if (mainWindow === null) {
    createWindow()
    mainWindow.setThumbarButtons([])
  }
})