Views error - Deprecated function: strtotime(): Passing null to parameter #1 ($datetime)

[stpaultim]

Description of the bug

I'm getting this error in views.

Deprecated function: strtotime(): Passing null to parameter #1 ($datetime) of type string is deprecated in views_handler_field_date->render() (line 76 of /var/www/html/core/modules/views/handlers/views_handler_field_date.inc).

In this view, I'm using a relationship to get the submitted date of a referenced node.

I am assuming this might be a core issue, because of this Drupal 7 issue and patch.
https://www.drupal.org/project/views/issues/3319405

Steps To Reproduce

This is happening on an existing site with lots of configuration. I have not yet tried to recreate the problem on a simple fresh site. I will try to do so shortly.