title: Flatpickr: cant clear the input when adding enableTime option
body: <p>I'm using flatpickr in React, and I'm having an issue after adding <code>enableTime</code> option, which is when clearing the input it automatically resets the input's date value.</p>
  
  <p>Here's my code
  <a href="https://stackblitz.com/edit/react-y1nfj6" rel="nofollow noreferrer">stackblitz DatePicker</a></p>