Fix missing ref

Author: developit

src/index.js

@@ -8,6 +8,8 @@ const ESC = {
 	'&': '&'
 };
 
+const EMPTY = {};
+
 const HOP = Object.prototype.hasOwnProperty;
 
 let encodeEntities = s => String(s).replace(/[<>"&]/g, escapeChar);