Affiliate module not found

[shterev]

Hello I have installed your free version of the extension and I have the following issue:

string(72) "site_root_dir/catalog/model/affiliate/affiliate.php"
Fatal error: Uncaught exception 'Exception' with message 'Error: Could not load model affiliate/affiliate!'
in site_root_dir/system/storage/modification/system/engine/loader.php:90 Stack trace: #0
site_root_dir/catalog/controller/extension/module/d_quickcheckout.php(461): Loader->model('affiliate/affil...') #1
site_root_dir/catalog/controller/extension/module/d_quickcheckout.php(382): ControllerExtensionModuleDQuickcheckout->createOrder() #2
site_root_dir/catalog/controller/extension/module/d_quickcheckout.php(47): ControllerExtensionModuleDQuickcheckout->initialize() #3
[internal function]: ControllerExtensionModuleDQuickcheckout->index(Array) #4
site_root_dir/system/storage/modification/system/engine/action.php(79): call_user_func_array(Array, Array) #5
site_root_dir/system/storage/modification/system/engine/loader.php(48): Action->execute(Object(Registry), Array) #6
/home/obuvlqm3/public_html/mi in site_root_dir/system/storage/modification/system/engine/loader.php on line 90

I checked file catalog/controller/extension/module/d_quickcheckout.php on line 461.
where is this line $this->load->model('affiliate/affiliate');.

In the Open Cart with version 3.0.2.0 I dont have such model.

The version of your extension is 6.6.1

How I reproduced the problem:

With logged user in the url I have tracking param like : https://domain.com?tracking=code then I click on buy on some product, then I open my card and click on checkoit button. Then I see the error on top.

What should I do to fix this?