title: :empty selector on tbody tag
body: <p>Given the following table:</p>
  
  <pre><code>&lt;table id="incidents"&gt;
      &lt;thead&gt;
          &lt;tr&gt;
              &lt;th&gt;&lt;/th&gt;
          &lt;/tr&gt;
      &lt;/thead&gt;
      &lt;tbody&gt;
      &lt;/tbody&gt;
  &lt;/table&gt;
  </code></pre>
  
  <p>Using jQuery the following evaluate as <code>false</code>:</p>
  
  <pre><code>$("#incidents tbody").is(":empty")
  </code></pre>
  
  <p>I would like to use CSS to set the content to be a message:</p>
  
  <pre class="lang-css prettyprint-override"><code>#incidents tbody:empty {
      content: "&lt;tr&gt;message foo&lt;/tr&gt;";
  }
  </code></pre>
  
  <p>Can the <code>:empty</code> selector be applied to tbody?</p>