/** @return */
 public static ContextImage getInvisibleDummyImage(
     final String id, final RequestCycle requestCylce) {
   final ContextImage image =
       new ContextImage(id, WicketUtils.getImageUrl(requestCylce, WebConstants.IMAGE_SPACER));
   image.setVisible(false);
   return image;
 }
 /** @see WicketUtils#getImageUrl(org.apache.wicket.Response, String) */
 public String getImageUrl(final String subpath) {
   return WicketUtils.getImageUrl(getRequestCycle(), subpath);
 }