make options argument optional

lib/hls-reader.js

@@ -42,6 +42,8 @@ function HlsReader(segmentReader, options) {
   if (!(this instanceof HlsReader))
     return new HlsReader(segmentReader, options);
 
+  options = options || {};
+
   Readable.call(this, { lowWaterMark: options.lowWaterMark, highWaterMark: options.highWaterMark });
 
   var self = this;