etl: fixed issue with user_logged_in_to_guest column null handling

etl did not handle null values well, this is now fixed.

Change-Id: I63a336b2b848ab6ae5431aff8ab00e2b83a45695
Bug-Url: https://bugzilla.redhat.com/1057412
Signed-off-by: Yaniv Dary <ydary@redhat.com>