I have a view which has a relationship to a referencing entity. I only want to include fields from the referencing entity in the display, but if I do not include a field from the current entity the following error occurs:

An AJAX HTTP error occurred.
HTTP Result Code: 500
Debugging information follows.
Path: /admin/structure/views/view/uexx_programm/preview/default/ajax
StatusText: Service unavailable (with message)
ResponseText: EntityMalformedException: Missing bundle property on entity of type node. in entity_extract_ids() (line 7633 of /opt/drupal/usr/share/drupal/7/includes/common.inc).

I attach an annotated PNG of the view's definition page to illustrate the error.