EDIT: Problem was solved by enabling second language 
(1/1) ContextErrorException
Notice: Undefined index: reduction_without_tax
in Cart.php line 792
at CartCore->getProducts(true)in CartPresenter.php line 319
at CartPresenter->present(object(Cart))in FrontController.php line 490
at FrontControllerCore->assignGeneralPurposeVariables()in FrontController.php line 548
at FrontControllerCore->initContent()in IndexController.php line 37
at IndexControllerCore->initContent()in Controller.php line 292
at ControllerCore->run()in Dispatcher.php line 515
at DispatcherCore->dispatch()in index.php line 28
Prestasho 1.7.6.4
Php 7.2.29
Does anyone have a clue or lead how to solve it? When i hit add to cart button nothing happens if i reafresh page i get this error.
I have custom theme and modul that allow clients to use decimal values and overwrites prices and quantities. With developer of modul we are trying to solve from 2 weeks but with no success.