Error: Call to a member function getTargetEntityTypeId() on null in fullcalendar_views_pre_view(

[socialnicheguru]

https://mysite.com/admin/structure/views/view/group_events/preview/sng_event_fullcalendar?_wrapper_format=drupal_ajax|https://mysite.com/admin/structure/views/view/group_events/edit/sng_event_fullcalendar|1||

Error: Call to a member function getTargetEntityTypeId() on null in fullcalendar_views_pre_view() (line 73 of drupal-8.4.4/html/modules/download/fullcalendar/fullcalendar.views_execution.inc

I am using http://drupal.org/project/date_recur
I have defined it as a Date (simple) field https://www.drupal.org/project/date_recur/issues/2846298#comment-12405009

I am not sure why it does not have a name attribute