code: public static URL getGridHubUrl() {
  		String value = getOptionalProperty(PROP_GRID_HUB_URL);
  		return (value == null) ? null : PropertiesUtils.toURL(value);
  	}
docs: @return a {@link URL} with the property {@value #PROP_GRID_HUB_URL};
  null, if not defined.
  
  @see PropertiesUtils#toURL(String)