Problem with is_active_sidebar?

Please try this one,because without id we i don’t think that will work:

  function reg_l_sid()
  {
   $args = array( 'id' => 'sidebar-footer-6','name'=> 'Left-sidebar');
   register_sidebar($args);
  }
  add_action('widgets_init', 'reg_l_sid');

and inside template:

  if (is_active_sidebar('sidebar-footer-6')) {
        dynamic_sidebar('sidebar-footer-6');
   } else {
        echo 'Please add widgets';
   }