Fixed application locale

app/controllers/application_controller.rb

@@ -147,6 +147,7 @@ class ApplicationController < ActionController::Base
     session[:locale] = params[:locale] if params[:locale]
     browser_locale = condition = nil
     default_locale = condition = nil
+    backup_locale = condition = nil
 
     # check if locale is valid for non site pages
     if LIST[:forbidden_item_names].include?(env['PATH_INFO'].split('/')[1].to_s)
@@ -161,9 +162,11 @@ class ApplicationController < ActionController::Base
       #check enable langauge detection
       browser_locale = request.env['HTTP_ACCEPT_LANGUAGE'].scan(/^[a-z]{2}/).first rescue nil
       condition = @site.in_use_locales.include?(browser_locale)
+    elsif (@site.default_locale.nil? && @site.enable_language_detection.eql?(false))
+      condition = @site.valid_locales.first
     end
 
-    session[:locale] = condition ? (browser_locale || session[:locale] || default_locale) : I18n.default_locale.to_s
+    session[:locale] = condition ? (browser_locale || session[:locale] || default_locale || backup_locale) : I18n.default_locale.to_s
     I18n.locale = session[:locale].to_sym
     @site_in_use_locales = @site.in_use_locales
     @site_valid_locales = site_locales_default_head(@site.valid_locales)