title: Input value for search filter disappears in Select ant design
body: <p>I am using <code>Ant Design</code> in my React app.</p>
  <p>In my Select Component I set showSearch to true.</p>
  <pre><code>&lt;Select
      showSearch={true}
      mode=&quot;multiple&quot;
      ... 
  </code></pre>
  <p>Input value for search disappears after I selected one of the options. I'd like to search/filter e.g. <code>London</code> and be able to click several options at one search.</p>
  <p>How can I do it?</p>