TypeError: Drupal\Core\Field\WidgetBase::getWidgetState(): Argument #1 ($parents) must be of type array, null given

Problem/Motivation

From time to time I see the following error in the logs:

TypeError: Drupal\Core\Field\WidgetBase::getWidgetState(): Argument #1 ($parents) must be of type array, null given, called in /app/docroot/modules/contrib/multiple_fields_remove_button/multiple_fields_remove_button.module on line 38 in Drupal\Core\Field\WidgetBase::getWidgetState() (line 600 of /app/docroot/core/lib/Drupal/Core/Field/WidgetBase.php)

Steps to reproduce

I am not sure how to reproduce it, I assume it is related to the us of Autosave Form → .

Proposed resolution

Ensure value is set for $field_name and $parents in multiple_fields_remove_button_submit_handler.