Merged PR 54136: Fix exception in OrderSaveAfter

## What's being changed

We're adding logic to prevent `unserialize()` of a null value in our OrderSaveAfter observer. We've also fixed an incorrect path reference in system.xml.

## Why it's being changed

In Magento 2.4.4-p1, [this change](magento/magento2@ad3e3cb#diff-35a4a7acd91fd572ad6de52c1030de9e9f047275a9590f98b2a66871ffcc444d) means that if no order status automations are set, there is an exception thrown each time an order is saved.

## How to review / test this change

- Ensure order status automations are empty
- Save an order (e.g. change its status from the admin)
- See no exception
- Add an order status automation for e.g. 'Processing'
- Save an order again (set it to 'Processing')
- Confirm that the contact is marked as not imported
- Confirm that the automation is queued

Related work items: #254722

Observer/Sales/OrderSaveAfter.php

@@ -319,6 +319,10 @@ private function statusCheckAutomationEnrolment($order, $status, $customerEmail,
             $storeId
         );
 
+        if (null === $orderStatusAutomations) {
+            return;
+        }
+
         try {
             $configStatusAutomationMap = $this->serializer->unserialize($orderStatusAutomations);
             if (!is_array($configStatusAutomationMap)) {

etc/config.xml

@@ -67,7 +67,7 @@
                 <first_order_automation>0</first_order_automation>
             </visitor_automation>
             <order_status_automation>
-                <status_to_automation></status_to_automation>
+                <program></program>
             </order_status_automation>
             <review_settings>
                 <enabled>0</enabled>