bug fixes for user_stat extraction, decrease querying

app/serializers/invited_user_serializer.rb

@@ -8,8 +8,19 @@ class InvitedUserSerializer < BasicUserSerializer
              :days_since_created
 
   def time_read
-    return nil if object.time_read.blank?
-    AgeWords.age_words(object.time_read)
+    AgeWords.age_words(object.user_stat.time_read)
+  end
+
+  def days_visited
+    object.user_stat.days_visited
+  end
+
+  def topics_entered
+    object.user_stat.topics_entered
+  end
+
+  def posts_read_count
+    object.user_stat.posts_read_count
   end
 
   def days_since_created

app/serializers/post_stream_serializer_mixin.rb

@@ -13,7 +13,7 @@ module PostStreamSerializerMixin
     return @posts if @posts.present?
     @posts = []
     @highest_number_in_posts = 0
-    if object.posts.present?
+    if object.posts
       object.posts.each_with_index do |p, idx|
         @highest_number_in_posts = p.post_number if p.post_number > @highest_number_in_posts
         ps = PostSerializer.new(p, scope: scope, root: false)