title: Best way to determine whether a XML attribute exists in Flex
body: <p>I have a XML response from an HTTPService call with the e4x result format.</p>
  
  <pre>
  <code>
  &lt;?xml version="1.0" encoding="utf-8"?>
  &lt;Validation Error="Invalid Username/Password Combination" />
  </code>
  </pre>
  
  <p>I have tried:</p>
  
  <pre>
  <code>
  private function callback(event:ResultEvent):void {
      if(event.result..@Error) {
          // error attr present
      }
      else {
          // error attr not present
      }
  }
  </code>
  </pre>
  
  <p>This does not seem to work (it always thinks that the error attribute exits) what is the best way to do this? thanks.</p>
  
  <p><b>EDIT:</b> I have also tried to compare the attribute to null and an empty string without such success...</p>