title: Placeholder text in chosen plugin for multiple select not working
body: <p>I'm working with a chosen multiple select. I'm trying to add a placeholder text for the select with <code>data-placeholder</code> attribute, but it doesn't fully work.</p>
  
  <p>The placeholder appears only after a click is performed on the select input and then out of it.</p>
  
  <p>I tried to put an empty option in the select as suggested for single selects in <a href="https://stackoverflow.com/questions/20200638/placeholder-text-for-chosen-plugin-for-single-select-not-working">this post</a>, but it didn't work.</p>
  
  <p>Does anybody have a solution?</p>
  
  <p>Here is my code</p>
  
  <pre><code>&lt;select id="mySelect" data-placeholder="Choose an option ..." class="chosen-select allow_additem item_to_upper" multiple tabindex="4"&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p>The select is filled with javascript.</p>