PHP errors when trying to change the view mode of sub landing page teasers

[andybroomfield]

This was discovered on the BHCC version of the LinkNodeReference in localgov_services_sublanding
(Actully the BHCC formatter that extends it).

Getting PHP errors when trying to set the view mode

Warning: Undefined array key "topic_list_term" in /Users/Andy/Sites/bhcclocalgov/docroot/core/modules/field_ui/src/Form/EntityDisplayFormBase.php on line 594

Warning: Trying to access array offset on value of type null in /Users/Andy/Sites/bhcclocalgov/docroot/core/modules/field_ui/src/Form/EntityDisplayFormBase.php on line 596

Warning: Trying to access array offset on value of type null in /Users/Andy/Sites/bhcclocalgov/docroot/core/modules/field_ui/src/Form/EntityDisplayFormBase.php on line 611

Warning: Trying to access array offset on value of type null in /Users/Andy/Sites/bhcclocalgov/docroot/core/modules/field_ui/src/Form/EntityDisplayFormBase.php on line 612

Warning: Trying to access array offset on value of type null in /Users/Andy/Sites/bhcclocalgov/docroot/core/modules/field_ui/src/Form/EntityDisplayFormBase.php on line 613

Warning: Undefined array key "search_api_excerpt" in /Users/Andy/Sites/bhcclocalgov/docroot/core/modules/field_ui/src/Form/EntityDisplayFormBase.php on line 624

Warning: Trying to access array offset on value of type null in /Users/Andy/Sites/bhcclocalgov/docroot/core/modules/field_ui/src/Form/EntityDisplayFormBase.php on line 624

Warning: Undefined array key "search_api_excerpt" in /Users/Andy/Sites/bhcclocalgov/docroot/core/modules/field_ui/src/Form/EntityDisplayFormBase.php on line 629

Warning: Trying to access array offset on value of type null in /Users/Andy/Sites/bhcclocalgov/docroot/core/modules/field_ui/src/Form/EntityDisplayFormBase.php on line 629

Warning: Undefined array key "search_api_excerpt" in /Users/Andy/Sites/bhcclocalgov/docroot/core/modules/field_ui/src/Form/EntityDisplayFormBase.php on line 630

Warning: Trying to access array offset on value of type null in /Users/Andy/Sites/bhcclocalgov/docroot/core/modules/field_ui/src/Form/EntityDisplayFormBase.php on line 630

There is no parent form call on the settingsForm method, adding $form = parent::settingsForm($form, $form_state); resolves the issue.