title: XSLT null comparison
body: <p>I have an xml as below.</p>
  
  <pre><code>&lt;attributes&gt;
          &lt;attribute&gt;
              &lt;attributeName&gt;agenda-group&lt;/attributeName&gt;
              &lt;value&gt;generic&lt;/value&gt;
          &lt;/attribute&gt;
          &lt;attribute&gt;
              &lt;attributeName&gt;auto-focus&lt;/attributeName&gt;
              &lt;value&gt;true&lt;/value&gt;
          &lt;/attribute&gt;
          &lt;attribute&gt;
              &lt;attributeName&gt;no-loop&lt;/attributeName&gt;
              &lt;value&gt;true&lt;/value&gt;
          &lt;/attribute&gt;
          &lt;attribute&gt;
              &lt;attributeName&gt;salience&lt;/attributeName&gt;
              &lt;value&gt;73&lt;/value&gt;
          &lt;/attribute&gt;
      &lt;/attributes&gt;
  </code></pre>
  
  <p>When i get the above  block i need to copy the above block as it is in resultant xml.If i get the below block with out values </p>
  
  <pre><code>   &lt;attributes&gt;
          &lt;attribute&gt;
              &lt;attributeName&gt;&lt;/attributeName&gt;
              &lt;value&gt;&lt;/value&gt;
          &lt;/attribute&gt;
  
      &lt;/attributes&gt;
  
           or
         &lt;attributes/&gt;
  </code></pre>
  
  <p>i need to omit this block in my resultant xml.I am using xslt for translation.
  Please provide some pointers to get the desired output.</p>