An added user appears twice in "Top Active Contributors" on an old and migrated subwiki

Steps to reproduce on an old wiki:

1. Create a wiki on 4.5.4 using this template xwiki/bin/view/XemManager/Install
2. Create a local user
3. Create a page with that local user (add some text and add some styles to it, e.g. bold, italic etc.)
4. Add an entry on an installed app (e.g. I installed Trip Planner)
5. Add some comments on Main.WebHome

Steps to reproduce after migration:

1. Go to the wiki created with the template
2. See the Top Active Contributors

Datebase: hypersql