客人结账后Prestashop 1.6.1.1空车

I enabled guest checkout but after checkout I get popup with message that my cart is empty! :-( Product allow buying by Guest, I've checked it out. I can't find place in prestachop code witch responsible for empty my cart. I supose it happen with JQuery and AJAX because message apears without page reloading. How to check for what is acctually happen with cart object using firebug or other debuging tool?

I created logger function and i'm trying to find out when cart becomes empty but it happens suddenly.

controllers\front\OrderOpcController.php

    class OrderOpcControllerCore extends ParentOrderController
{
[...]
public function init()
        {
            parent::init();
    [...]

    LoggerClass::MyLogger($this->context->cart, __LINE__);

When I add my first product to cart then I get follwing output:

Cart Object
(
    [id] => 1872
    [id_shop_group] => 1
    [id_shop] => 1
    [id_address_delivery] => 0
    [id_address_invoice] => 0
    [id_currency] => 1
    [id_customer] => 0
    [id_guest] => 5446
    [id_lang] => 7
    [recyclable] => 0
    [gift] => 0
    [gift_message] => 
    [mobile_theme] => 0
    [date_add] => 2016-02-06 00:18:59
    [secure_key] => 
    [id_carrier] => 0
    [date_upd] => 2016-02-06 00:19:00
    [checkedTos] => 
    [pictures] => 
    [textFields] => 
    [delivery_option] => 
    [allow_seperated_package] => 0
    [_products:protected] => Array
        (
            [0] => Array
                (
                    [id_product_attribute] => 31
                    [id_product] => 22
                    [cart_quantity] => 1
                    [id_shop] => 1

[...]

but after positive guest checkout I get message that my cartis empty and output is for empty cart too

Cart Object
(
    [id] => 
    [id_shop_group] => 1
    [id_shop] => 1
    [id_address_delivery] => 0
    [id_address_invoice] => 0
    [id_currency] => 1
    [id_customer] => 
    [id_guest] => 0
    [id_lang] => 7
    [recyclable] => 0
    [gift] => 0
    [gift_message] => 
    [mobile_theme] => 
    [date_add] => 
    [secure_key] => 
    [id_carrier] => 0
    [date_upd] => 
    [checkedTos] => 
    [pictures] => 
    [textFields] => 
    [delivery_option] => 
    [allow_seperated_package] => 
    [_products:protected] => 

[...]

SAVEbutton not disappears but message Account information saved successfully is showing.