title: Antd Date : how to set valid empty date in moment js
body: <p>I am using ANTD (<a href="https://ant.design/" rel="nofollow noreferrer">https://ant.design/</a>) for the project, ANTD is working fine with other components whereas I am facing issue while using DatePicker(<a href="https://ant.design/components/date-picker/" rel="nofollow noreferrer">https://ant.design/components/date-picker/</a>).
  DatePicker uses moment(<a href="https://momentjs.com/" rel="nofollow noreferrer">https://momentjs.com/</a>)</p>
  
  <p>In a form initially, I want all the fields with a placeholder and once the user fills the form it will be displayed to him/her. Once added user can edit their data.</p>
  
  <p>Setting data works fine but I am unable to set date field initially as empty so that I am able to show the user a field with a placeholder</p>
  
  <p>I am setting the date field as</p>
  
  <pre><code>initialValue: moment(null) =&gt; invalid date
  initialValue: moment('') =&gt; invalid date
  initialValue: moment(undefined) =&gt; current date // i don't want current date i want empty (to show the placeholder instead)
  </code></pre>
  
  <p>where as when i am getting user selected while setting the date it works perfectly fine.</p>
  
  <pre><code> initialValue: moment(userSelectedDate) =&gt;  user selected date
  </code></pre>