Fix assets list assigned an empty buffer (#444)

* Fix assets list assigned an empty buffer

* Add asset list join argument

Author: tornqvist

lib/graph-assets.js

@@ -36,7 +36,7 @@ function node (state, createEdge) {
 
   tracker.on('change', function () {
     var list = tracker.list()
-    createEdge('list', Buffer.from(list))
+    createEdge('list', Buffer.from(list.join(',')))
   })
 
   tracker.on('progress', function (progress) {