...

app/controllers/messages_controller.rb

@@ -99,7 +99,7 @@ class MessagesController < ApplicationController
           for teacher in teachers
             if(teacher.user_id != User.current.id)
               notify = ActivityNotify.new()
-              if(@board.course_id>0)
+              if(@board.course)
                 notify.activity_container_id = @board.course_id
                 notify.activity_container_type = 'Course'
               else
@@ -188,7 +188,7 @@ class MessagesController < ApplicationController
         notifyto_arr.each do |k,user_id|
           if(user_id != User.current.id)
             notify = ActivityNotify.new()
-            if(@board.course_id>0)
+            if(@board.course)
               notify.activity_container_id = @board.course_id
               notify.activity_container_type = 'Course'
             else