Bugfix/null classification store groups (#14909)

* check object exists before getting parent

* use is_null

---------

Co-authored-by: Cameron Jenkins <cameron.jenkins@torqit.ca>

models/DataObject/Classificationstore.php

@@ -511,7 +511,7 @@ private function getAllDataFromField(callable $mergeFunction): array
     {
         $fieldsArray = $mergeFunction($this, []);
         $object = $this->getObject();
-        while (($parent = Service::hasInheritableParentObject($object)) !== null) {
+        while (!is_null($object) && ($parent = Service::hasInheritableParentObject($object)) !== null) {
             $fieldDefintions = $parent->getClass()->getFieldDefinitions();
             foreach ($fieldDefintions as $key => $fd) {
                 if ($fd instanceof Model\DataObject\ClassDefinition\Data\Classificationstore) {