[bug fix] Make sure bundles is an array in loadBundlesLazy (#755)

* always add the bundle-loader module

* check if the asset is already in the bundle

* make sure bundles is an array in loadBundlesLazy

Author: albizures

src/builtins/bundle-loader.js

@@ -1,6 +1,10 @@
 var getBundleURL = require('./bundle-url').getBundleURL;
 
 function loadBundlesLazy(bundles) {
+  if (!Array.isArray(bundles)) {
+    bundles = [bundles]
+  }
+
   var id = bundles[bundles.length - 1];
 
   try {