Prevent WSOD when loading a store-orphaned order

Closes #3354205

modules/order/src/Entity/Order.php

@@ -665,7 +665,7 @@ class Order extends CommerceContentEntityBase implements OrderInterface {
    * {@inheritdoc}
    */
   public function getCalculationDate() {
-    $timezone = $this->getStore()->getTimezone();
+    $timezone = $this->getStore()?->getTimezone();
     $timestamp = $this->getPlacedTime() ?: \Drupal::time()->getRequestTime();
     $date = DrupalDateTime::createFromTimestamp($timestamp, $timezone);