Fix dark mode for users not logged in

app/helpers/application_helper.rb

@@ -4,7 +4,7 @@ module ApplicationHelper
     attributes[:loggedin_uid] = current_user.id if user_signed_in?
     attributes[:is_shiftcoordinator] = 1 if current_user&.shiftcoordinator?
     attributes[:languages_from] = current_user.languages_from unless current_user&.languages_from.blank?
-    attributes[:darkmode] = current_user.darkmode
+    attributes[:darkmode] = current_user&.darkmode || "auto"
     { data: attributes }
   end
 end