Update

-<?php
-
-namespace FGCT\OverrideCreateInvoice\Helper;
-
-class Data extends \Magento\Framework\App\Helper\AbstractHelper {
-	protected $_filesystem;
-	protected $_directory_list;
-	protected $_resource;
-	protected $_scopeConfig;
-    public function __construct(
-        \Magento\Framework\App\Helper\Context $context,
-		\Magento\Framework\Filesystem $filesystem,
-		\Magento\Framework\App\ResourceConnection $resource,
-		\Magento\Framework\App\Config\ScopeConfigInterface $scopeConfig,
-        \Magento\Framework\App\Filesystem\DirectoryList $directory_list
-    ) {
-		parent::__construct($context);
-		$this->_filesystem = $filesystem;
-        $this->_directory_list = $directory_list;
-		$this->_resource = $resource;
-		$this->_scopeConfig = $scopeConfig;
-	}
-}

@@ -28,16 +28,15 @@ class OrderInvoiceSaveBefore implements ObserverInterface {
 		$objectManager = \Magento\Framework\App\ObjectManager::getInstance();
 		$orderId = $this->_request->getParam('order_id');
 		$invoice = $observer->getEvent()->getInvoice();
-		$order = $invoice->getOrder();
+		// $order = $invoice->getOrder();
 		$productManager = $objectManager->create('Magento\Catalog\Model\Product');
 		$productsOutStock = $productsNotEnoughQty = [];
 		foreach ($invoice->getAllItems() as $item) {
 			$name = $item->getName();
-			$type = $item->getSku();
+			// $type = $item->getSku();
 			$productId = $item->getProductId();
 			$qty = $item->getQty();
-			$product = $productManager->load($productId);
-
+			// $product = $productManager->load($productId);
 			$_productStock = $this->_stockItemRepository->get($productId);
 			// $_productStock->getQty();
 			if(!$_productStock->getIsInStock()) {