Make new dependency optional

Author: kassner

app/code/Magento/Catalog/Controller/Adminhtml/Product/Initialization/Helper.php

@@ -97,7 +97,7 @@ public function __construct(
         \Magento\Catalog\Model\Product\Initialization\Helper\ProductLinks $productLinks,
         \Magento\Backend\Helper\Js $jsHelper,
         \Magento\Framework\Stdlib\DateTime\Filter\Date $dateFilter,
-        \Magento\Catalog\Model\Product\LinkTypeProvider $linkTypeProvider
+        \Magento\Catalog\Model\Product\LinkTypeProvider $linkTypeProvider = null
     ) {
         $this->request = $request;
         $this->storeManager = $storeManager;