Localization error when using FriendsOfCake/Search plugin

Hello, I set up searching on my site according to the CakePHP CookBook - Internationalization & Localization - 4.x and localization was working. Here are two screenshots:

This is page in English:

This is page in Slovak:

Switching between languages was implemented using the GET method (default locale is sent as a parameter of GET FORM).

When I add search functionality using the FriendsOfCake/Search plugin, the site crashes on language change.

This is my AppController:

This is my index.php View template:

This is page running in default language and active search module:

The site crushes when I switch the language:

This is the error:

Can please anybody help me, how to fix this issue?

Thank you.