Error when I click on the blog post comment to moderate from the My tasks gadget

Steps to reproduce:

1. Create a blog with moderation set to "beforehand".
2. Add a blog post.
3. Give a user the right to comment.
4. With this user, add a comment on the blog post (from the WebEngine UI).
5. With Administrator, go on your dashboard and click on the blog post from the My tasks gadget.
   => You get an error.
6. Try to go on the blog post using regular browsing.
   => You get an error when you click on the post from the blog DM UI.

This bug is also happening when displaying tasks created with CreateTask operation.