Refactored the website_ids array

Author: eduard13

app/code/Magento/Catalog/Model/Product.php

@@ -810,7 +810,8 @@ public function getStoreIds()
         if (!$this->hasStoreIds()) {
             $storeIds = [];
             if ($websiteIds = $this->getWebsiteIds()) {
-                foreach ($websiteIds as $websiteId => $selectedId) {
+                $websiteIds = array_keys($websiteIds);
+                foreach ($websiteIds as $websiteId) {
                     $websiteStores = $this->_storeManager->getWebsite($websiteId)->getStoreIds();
                     $storeIds = array_merge($storeIds, $websiteStores);
                 }