ACP2E-1650:Create Shipment API

- addressed CR issue

Author: aplapana

app/code/Magento/Sales/Model/Order/Shipment/Item.php

@@ -389,16 +389,18 @@ public function setExtensionAttributes(\Magento\Sales\Api\Data\ShipmentItemExten
      */
     private function loadChildren(): void
     {
-        $collection = $this->_orderItem->getOrder()->getItemsCollection();
-        $collection->filterByParent($this->_orderItem->getItemId());
-
-        if ($collection->count()) {
-            $this->_orderItem->setData('has_children', true);
-
-            /** @var \Magento\Sales\Model\Order\Item $childItem */
-            foreach ($collection as $childItem) {
-                if ($childItem->getItemId() != $this->_orderItem->getItemId()) {
-                    $this->_orderItem->addChildItem($childItem);
+        if ($this->_orderItem) {
+            $collection = $this->_orderItem->getOrder()->getItemsCollection();
+            $collection->filterByParent($this->_orderItem->getItemId());
+
+            if ($collection->count()) {
+                $this->_orderItem->setData('has_children', true);
+
+                /** @var \Magento\Sales\Model\Order\Item $childItem */
+                foreach ($collection as $childItem) {
+                    if ($childItem->getItemId() != $this->_orderItem->getItemId()) {
+                        $this->_orderItem->addChildItem($childItem);
+                    }
                 }
             }
         }