FEATURE: do not redirect to top page when number of topis is low

app/serializers/site_serializer.rb

@@ -9,7 +9,8 @@ class SiteSerializer < ApplicationSerializer
              :top_menu_items,
              :anonymous_top_menu_items,
              :uncategorized_category_id, # this is hidden so putting it here
-             :is_readonly
+             :is_readonly,
+             :has_enough_topic_to_redirect_to_top_page
 
   has_many :categories, serializer: BasicCategorySerializer, embed: :objects
   has_many :post_action_types, embed: :objects
@@ -50,4 +51,12 @@ class SiteSerializer < ApplicationSerializer
     Discourse.readonly_mode?
   end
 
+  def has_enough_topic_to_redirect_to_top_page
+    Topic.listable_topics
+         .visible
+         .includes(:category).references(:category)
+         .where('COALESCE(categories.topic_id, 0) <> topics.id')
+         .count > SiteSetting.topics_per_period_in_top_page
+  end
+
 end