Remove another N+1 query from categories page

app/models/category_list.rb

@@ -40,6 +40,7 @@ class CategoryList
       @topics_by_id = {}
 
       @all_topics = Topic.where(id: category_featured_topics.map(&:topic_id))
+      @all_topics = @all_topics.includes(:last_poster) if include_latest_posts?
       @all_topics.each do |t|
         t.include_last_poster = true if include_latest_posts? # hint for serialization
         @topics_by_id[t.id] = t