Fix responding to commit notes

app/mailers/notify.rb

@@ -49,9 +49,19 @@ class Notify < ActionMailer::Base
   def sent_notification!(noteable, recipient_id)
     return unless reply_key
+    noteable_id = nil
+    commit_id = nil
+    if noteable.is_a?(Commit)
+      commit_id = noteable.id
+    else
+      noteable_id = noteable.id
+    end
+
     SentNotification.create(
       project:        noteable.project,
-      noteable: noteable,
+      noteable_type:  noteable.class.name,
+      noteable_id:    noteable_id,
+      commit_id:      commit_id,
       recipient_id:   recipient_id,
       reply_key:      reply_key
     )