Remove body_class_string helper (#33072)

app/controllers/application_controller.rb

@@ -22,7 +22,6 @@ class ApplicationController < ActionController::Base
   helper_method :use_seamless_external_login?
   helper_method :sso_account_settings
   helper_method :limited_federation_mode?
-  helper_method :body_class_string
   helper_method :skip_csrf_meta_tags?
 
   rescue_from ActionController::ParameterMissing, Paperclip::AdapterRegistry::NoHandlerError, with: :bad_request
@@ -158,10 +157,6 @@ class ApplicationController < ActionController::Base
     current_user.setting_theme
   end
 
-  def body_class_string
-    @body_classes || ''
-  end
-
   def respond_with_error(code)
     respond_to do |format|
       format.any  { render "errors/#{code}", layout: 'error', status: code, formats: [:html] }

app/helpers/application_helper.rb

@@ -143,7 +143,7 @@ module ApplicationHelper
   end
 
   def body_classes
-    output = body_class_string.split
+    output = []
     output << content_for(:body_classes)
     output << "theme-#{current_theme.parameterize}"
     output << 'system-font' if current_account&.user&.setting_system_font_ui