#3314765-2: Add an access check before setting.

field_list_details.module

@@ -42,6 +42,8 @@ function field_list_details_theme() {
  * Implements hook_entity_type_alter().
  */
 function field_list_details_entity_type_alter(array &$entity_types) {
-  $entity_types['field_config']->setListBuilderClass('Drupal\field_list_details\FieldListDetailsFieldConfigListBuilder');
+  if (!is_null($entity_types['field_config'])) {
+    $entity_types['field_config']->setListBuilderClass('Drupal\field_list_details\FieldListDetailsFieldConfigListBuilder');
+  }
   $entity_types['entity_form_display']->setFormClass('edit', 'Drupal\field_list_details\FieldListDetailsEntityFormDisplayEditForm');
 }