FIX: You could update a topic to have a title that's too short if the TextCleaner

removed extra characters. Additionally, updating the title will not return an error
message to the client app if the operation fails (rather than failing silently.)

app/controllers/topics_controller.rb

@@ -62,14 +62,19 @@ class TopicsController < ApplicationController
       topic.archetype = "regular" if params[:archetype] == 'regular'
     end
 
+    success = false
     Topic.transaction do
-      topic.save
-      topic.change_category(params[:category])
+      success = topic.save
+      topic.change_category(params[:category]) if success
     end
 
     # this is used to return the title to the client as it may have been
     # changed by "TextCleaner"
-    render_serialized(topic, BasicTopicSerializer)
+    if success
+      render_serialized(topic, BasicTopicSerializer)
+    else
+      render_json_error(topic)
+    end
   end
 
   def similar_to