Steps to Reproduce
1. Prepare OOTB Alfresco v5.1.1.
2. Upload an avatar picture for the admin user.
3. Now you can see the picture file in the “My files” dashlet. (You may need to wait a little and reload them.)
4. Click on this picture and make a comment.
5. Go back to the user home page.
In the “My activities” dashlet the activities with the “@@NULL@@” site. See screenshot NULL.PNG
No site link if the item does not belong to the site.