add a missing check for an undefined object

lms/templates/shoppingcart/shopping_cart.html

@@ -208,7 +208,7 @@ from django.utils.translation import ugettext as _
        // before going to billing details page
        // if exists then trigger click event of the apply code button
        var code = $('div.code-input input#input_code').val();
-       if (code!= ''){
+       if (typeof(code) != 'undefined' && code != ''){
           $('div.code-input #submit-code').trigger('click');
           return false;
        }