code: function isEmpty( node ) {
  		return node.type == CKEDITOR.NODE_TEXT &&
  			!CKEDITOR.tools.trim( node.value ) ||
  			node.type == CKEDITOR.NODE_ELEMENT &&
  			node.attributes[ 'data-cke-bookmark' ];
  	}
docs: Judge whether the node is an ghost node to be ignored, when traversing.