Uninitialized constant error (possible new Rails issue)

Attempting to run GitLab from sources on Ubuntu 18.04 with non-default directory structure, the following error I encounter every time when I try to request a webpage:

Started GET "/gitlab/api/v4/internal/check" for 127.0.0.1 at 2018-06-16 09:31:18 +0000
Started GET "/gitlab/users/sign_in" for <IP address> at 2018-06-16 09:31:53 +0000
Processing by SessionsController#new as HTML
Completed 500 Internal Server Error in 14ms (ActiveRecord: 1.6ms)

ActionView::Template::Error (uninitialized constant ActionView::CompiledTemplates::EXPR_ARG):
    1: %ul.nav-links.new-session-tabs.nav-tabs.nav{ role: 'tablist' }
    2:   %li.nav-item{ role: 'presentation' }
    3:     %a.nav-link.active{ href: '#login-pane', data: { toggle: 'tab' }, role: 'tab' } Sign in
    4:   - if allow_signup?
  app/views/devise/shared/_tabs_normal.html.haml:1:in `_app_views_devise_shared__tabs_normal_html_haml___3183421741055724100_47281175216580'
  app/views/devise/sessions/new.html.haml:7:in `_app_views_devise_sessions_new_html_haml__998010156118485515_47281178420240'
  app/controllers/sessions_controller.rb:22:in `new'
  lib/gitlab/i18n.rb:50:in `with_locale'
  lib/gitlab/i18n.rb:56:in `with_user_locale'
  app/controllers/application_controller.rb:362:in `set_locale'
  lib/gitlab/middleware/multipart.rb:95:in `call'
  lib/gitlab/request_profiler/middleware.rb:14:in `call'
  lib/gitlab/middleware/go.rb:17:in `call'
  lib/gitlab/etag_caching/middleware.rb:11:in `call'
  lib/gitlab/middleware/read_only/controller.rb:28:in `call'
  lib/gitlab/middleware/read_only.rb:16:in `call'
  lib/gitlab/request_context.rb:18:in `call'
  lib/gitlab/metrics/requests_rack_middleware.rb:27:in `call'
  lib/gitlab/middleware/release_env.rb:10:in `call'

I do not know Ruby well, so I have no idea about suitable workaround. Google and StackOverflow told that it may be Rails issue. I also use SSL and Apache with relative URL schema (it is not possible to use Nginx because of hoster restrictions). How can I fix the described error?