Nightmare forced to stop?

Question

JavaScript

I have code like this how to stop running when

if(window.document.querySelector('#validate') === null)

nightmare.goto('https://').wait(2000)
  .evaluate(() => {
    if(window.document.querySelector('#validate') === null)
    {
      return this.end();
    }
  })
  .type('#validateInput', 'Hello World!')
  .click('#validateButton')
  .wait(2000)
  .end()
  .catch(e => {
    console.error(e);
  });