driver.BatchCursor Next returns true when first batch is empty

The comment for driver.BatchCursor.Next(context.Context) says "This method will return false when an empty batch is returned." However, if the first batch is empty, it returns true. This ticket should make Next return false when bc.firstBatch is true and the batch is empty; this is the problematic code: https://github.com/mongodb/mongo-go-driver/blob/24c422eb6da5e148e55df79804a7058fa322979f/x/mongo/driver/batch_cursor.go#L167