parent().css failing in IE - simple jquery

parent().css failing in IE - simple jquery

Hi All,
 
I have an extremely simple Jquery function that is failing in IE...
 
  1. $(document).ready(function() {
  2.   $("ul.sub-menu").parent("li.menu-item").css("background-image", "url(images/nav/navBar_60orangeSubDN.jpg");
  3.  });
    This simple code results in an error on line 4618 of jquery-4.1.2.js....
    The fail code is:
    if ( set ) {
       style[ name ] = value;
      }