Username returning empty

Here is an example of what is returned as a tweet:

{'id': '815709183261769729', 'permalink': 'https://twitter.com/rachaelsibs/status/815709183261769729', 'username': '', 'text': "so no they don't all count... that's just a total number of white men who died in the civil war.", 'date': datetime.datetime(2017, 1, 1, 18, 59, 59), 'formatted_date': 'Sun Jan 01 18:59:59 +0000 2017', 'retweets': 0, 'favorites': 0, 'mentions': '', 'hashtags': '', 'geo': '', 'urls': '', 'author_id': 799595761004662784}

Not all tweets are geotagged but all tweets should have a username.