prevent a case of multiple callbacks

lib/storage/blob.js

@@ -378,7 +378,10 @@ var makeWalker = function (n, handleChild, done) {
             nThen(function (w) {
                 // check if the path is a directory...
                 Fs.stat(path, w(function (err, stats) {
-                    if (err) { return next(); }
+                    if (err) {
+                        w.abort();
+                        return next();
+                    }
                     if (!stats.isDirectory()) {
                         w.abort();
                         return void handleChild(void 0, path, next);