mautic.ERROR: PHP Error: Argument 1

I am getting this error below when attempting to send an e-mail.



Any idea how I can fix this? It was sending properly before.



[2016-02-29 19:54:30] mautic.ERROR: PHP Error: Argument 1 passed to MauticCoreBundleEntityIpAddress::setDoNotTrackList() must be of the type array, null given, called in /home/click/public_html/clients/legal/3/app/bundles/CoreBundle/Factory/MauticFactory.php on line 660 and defined - in file /home/click/public_html/clients/legal/3/app/bundles/CoreBundle/Entity/IpAddress.php - at line 151 [] []

I am getting this error below when attempting to send an e-mail.

Any idea how I can fix this? It was sending properly before.

[2016-02-29 19:54:30] mautic.ERROR: PHP Error: Argument 1 passed to MauticCoreBundleEntityIpAddress::setDoNotTrackList() must be of the type array, null given, called in /home/click/public_html/clients/legal/3/app/bundles/CoreBundle/Factory/MauticFactory.php on line 660 and defined - in file /home/click/public_html/clients/legal/3/app/bundles/CoreBundle/Entity/IpAddress.php - at line 151 [] []

Can you provide steps to replicate?