Error Encountered: Call to a member function getValue() on null in Drupal\Core\Field\FieldItemList->getEntity()

Hmm, I can reproduce it using the WebformOfficeHours element.
Test:
- enable Webform + WebForm UI
- create a Webform with an Office Hours element
- create a submission
- check the submission via admin/structure/webform/manage/TYPE/results/submissions

Above patch fixes the problem when displaying a Webform Submission with WebFormOfficeHours.
It is rather big - working on other issues as well.

Main change is this, adding a parent:

-  protected function unserialize(array $office_hours, array $element) {
+  protected function unserialize(array $office_hours, array $element, WebformSubmissionInterface $webform_submission) {
-    /** @var \Drupal\Core\Field\FieldItemListInterface $items */
-    $items = \Drupal::typedDataManager()
-      ->create($this->getFieldDefinition($element));
-
...
+    /** @var \Drupal\Core\Field\FieldItemListInterface $items */
+    $items = \Drupal::typedDataManager()
+      ->create($this->getFieldDefinition(),
+        $values,
+        $element['#webform_key'],
+        $webform_submission->getTypedData()
+      );
+    $items->filterEmptyItems();
     return $items;
   }

@original posters,
please share debug_backtrace(), so I can better check the root cause of your problem (or report back when the above change has successfully removed the error.)

Automatically closed - issue fixed for 2 weeks with no activity.