Bug with bluebird and promisify [Fixed but don't know how to pull request]

[nvarcha]

I was getting an error: Unhandled rejection TypeError: expecting an array or an iterable object but got [object Null]

According to this, the method signature changed.

So I changed the tree.js file like so:
Line 80 was:

streamWorker(cursor.stream(), numWorkers, function streamOnData(doc, done) {

                            var newPath = self.path + doc.path.substr(previousPath.length);
                            self.collection.update({ _id: doc._id }, { $set: { path: newPath } }, done);
                        },
                        next);

I changed to:

 streamWorker(cursor.stream(), function streamOnData(doc, done) {

                            var newPath = self.path + doc.path.substr(previousPath.length);
                            self.collection.update({ _id: doc._id }, { $set: { path: newPath } }, done);
                        },
                            {concurrency: numWorkers},
                        next);

I'm sorry I'm pretty new and I don't know how to create a pull request with this.