Hotfix/2271 export csv data quality issues.

@aronasorman.

Issue: #2271 export csv data quality issues

We used Mikewray's data from staging and we found out that some of `completion_timestamp` column of `VideoLog` contains a null value. So we included that null value of `completion_timestamp` in `video_logs` query.

Screenshots are attached bellow.

**CSV report**
![CSV-Report](https://raw.githubusercontent.com/djallado/Files/master/CSV-Report.png)

**Web-view**
![web-view](https://raw.githubusercontent.com/djallado/Files/master/web-view.png)