code: public void appendOptionalUrlAttribute(final String name, final String value) {
  		if (value != null) {
  			appendUrlAttribute(name, value);
  		}
  	}
docs: <p>
  If the value is not null, add an xml attribute name+value pair to the end of this XmlStringBuilder
  <p>
  Eg. name="value"
  </p>
  
  @param name the name of the attribute to be added.
  @param value the value of the attribute.