[-] Core: Fix bad card context assignation

git-svn-id: http://dev.prestashop.com/svn/v1/branches/1.5.x@14236 b9a71923-0436-4b27-9f14-aed3839534dd

classes/Product.php

@@ -2274,7 +2274,8 @@ class ProductCore extends ObjectModel
 				die(Tools::displayError());
 			$cur_cart = new Cart($id_cart);
 			// Store cart in context to avoid multiple instantiations in BO
-			$context->cart = $cur_cart;
+			if (!Validate::isLoadedObject($context->cart))
+				$context->cart = $cur_cart;
 		}
 
 		$cart_quantity = 0;