// Fix for quantities update

classes/stock/StockAvailable.php

@@ -484,7 +484,10 @@ class StockAvailableCore extends ObjectModel
 				$stock_available->id_product_attribute = (int)$id_product_attribute;
 				$stock_available->quantity = (int)$quantity;
 
-				$shop_group = new ShopGroup((int)Shop::getGroupFromShop((int)$id_shop));
+				if ($id_shop === null)
+					$shop_group = Shop::getContextShopGroup();
+				else
+					$shop_group = new ShopGroup((int)Shop::getGroupFromShop((int)$id_shop));
 		
 				// if quantities are shared between shops of the group
 				if ($shop_group->share_stock)