FIX: don't double add users to topic allowed users

In latest rails building the same relation twice results in an error
Previous versions would deduplicate

lib/topic_creator.rb

@@ -190,9 +190,13 @@ class TopicCreator
     add_users(topic, @opts[:target_usernames])
     add_emails(topic, @opts[:target_emails])
     add_groups(topic, @opts[:target_group_names])
+
+    if !@added_users.include?(user)
       topic.topic_allowed_users.build(user_id: @user.id)
     end
 
+  end
+
   def save_topic(topic)
     topic.disable_rate_limits! if @opts[:skip_validations]
 
@@ -228,8 +232,10 @@ class TopicCreator
         display_name = email.split("@").first
 
         if user = find_or_create_user(email, display_name)
+          if !@added_users.include?(user)
             @added_users << user
             topic.topic_allowed_users.build(user_id: user.id)
+          end
           len += 1
         end
       end