title: DOM PDF is displaying an error message if " <thread> </thread>" is used in HTML
body: <p>I am trying to create PDF using DOMPDF. When I use the following in my HTML it shows an error message and doesn't create any pdf.</p>
  
  <pre><code>    &lt;thead&gt;
      &lt;th&gt;First Name&lt;/th&gt;
      &lt;th&gt;Last Name&lt;/th&gt;
      &lt;th&gt;Email Address&lt;/th&gt;
      &lt;th&gt;Website&lt;/th&gt;
   &lt;/thead&gt;
  </code></pre>
  
  <p>The Error Message</p>
  
  <p>Severity: Notice</p>
  
  <p>Message: Array to string conversion</p>
  
  <p>Filename: include/style.cls.php</p>
  
  <p>Line Number: 948</p>
  
  <p>Fatal error: Call to undefined method DOMText::getAttribute() in C:...</p>
  
  <p>Do you have any idea how to get rid of this problem?</p>
  
  <p>Thanks in Advance :)</p>