Why does ubuntu 18 04 completely freeze after User Themes?

Question

css

I decided to change the theme by going to the site https://extensions.gnome.org/ and finding User Themes downloaded the files, and by clicking on On, the site hangs completely, ubuntu too. It hangs so that even changing the language and force closing does not work, only the cursor works (only drive, you can’t click). GNOME 3.30. Version user themes 35.

Answer 1

$(document).ready(function(){                                                  
    $('.view-source .spisok').hide();
    $('.view-source a').on('click', function() {
      $(this).siblings('.spisok').stop().slideToggle(500);
    });
});

Answer 2

Ubuntu completely hangs after User Themes?

Maybe completely, maybe not completely. How are we supposed to know?