title: Oracle SELECT XMLELEMENT with Null
body: <p>Using Oracle 11, when I do  </p>
  
  <pre><code>  SELECT XMLELEMENT("dummy", NULL) as xml_1 
      FROM dual
  </code></pre>
  
  <p>The output is <code>&lt;dummy&gt;&lt;/dummy&gt;</code></p>
  
  <p>How can I force to return  <code>&lt;dummy /&gt;</code> ?</p>