Take new rows without subject_ids into account
Take new rows without subject_ids into account

Otherwise we would be trying to insert null values and failing the
constraints.

zooniverse/Panoptes,astopy/Panoptes,zooniverse/Panoptes,srallen/Panoptes,parrish/Panoptes,camallen/Panoptes,camallen/Panoptes,parrish/Panoptes,srallen/Panoptes,zooniverse/Panoptes,astopy/Panoptes,srallen/Panoptes,parrish/Panoptes,srallen/Panoptes,astopy/Panoptes,parrish/Panoptes,camallen/Panoptes,zooniverse/Panoptes,camallen/Panoptes,astopy/Panoptes