Issue #3457389: AssertionError: Cannot load the "file" entity with NULL ID

Closes #3457389

src/Plugin/Field/FieldType/CalendarDownloadType.php

@@ -186,8 +186,10 @@ class CalendarDownloadType extends FieldItemBase {
     // The current fielditem belongs to a fielditemlist,
     // that in turn belongs to a fieldable entity.
     $entity = $this->getParent()->getParent()->getValue();
-    $file = File::load($this->get('fileref')->getValue());
-    $this->fileUsageService->delete($file, 'ics_field', $entity->getEntityTypeId(), $entity->id());
+    if ($entity && $this->get('fileref')->getValue()) {
+      $file = File::load($this->get('fileref')->getValue());
+      $this->fileUsageService->delete($file, 'ics_field', $entity->getEntityTypeId(), $entity->id());
+    }
   }
 
   /**