Fix register page not showing right startup css

- We fixed this by passing a local from the devise
  layout to the startup_css partial which now signifies
  if we should load the sign_in startup or not

app/views/layouts/_head.html.haml

@@ -36,7 +36,7 @@
 
   = favicon_link_tag favicon, id: 'favicon', data: { original_href: favicon }, type: 'image/png'
 
-  = render 'layouts/startup_css'
+  = render 'layouts/startup_css', { startup_filename: local_assigns.fetch(:startup_filename, nil) }
   - if user_application_theme == 'gl-dark'
     = stylesheet_link_tag_defer "application_dark"
     = yield :page_specific_styles

app/views/layouts/_startup_css.haml

-- startup_filename = current_path?("sessions#new") ? 'signin' : user_application_theme == 'gl-dark' ? 'dark' : 'general'
+- startup_filename_default = user_application_theme == 'gl-dark' ? 'dark' : 'general'
+- startup_filename = local_assigns.fetch(:startup_filename, nil) || startup_filename_default
 
 %style
   = Rails.application.assets_manifest.find_sources("themes/#{user_application_theme_css_filename}.css").first.to_s.html_safe if user_application_theme_css_filename

app/views/layouts/devise.html.haml

 !!! 5
 %html.devise-layout-html{ class: system_message_class }
-  = render "layouts/head"
+  = render "layouts/head", { startup_filename: 'signin' }
   %body.ui-indigo.login-page.application.navless{ class: "#{client_class_list}", data: { page: body_data_page, qa_selector: 'login_page' } }
     = header_message
     = render "layouts/init_client_detection_flags"