Notifications from existing instance are not preserved anymore when upgrading XWiki

STEPS TO REPRODUCE

1. Create an older instance of XWiki (e.g. 11.10.5)
2. Login as Admin
3. Create an user (e.g. U1)
4. Login as U1
5. Go to Notifications > Settings
6. Set all Pages Notifications to ON (watch entire wiki)
7. Login as Admin
8. Create, update and comment some pages (to generate some events)
9. Login as U1 and observe the notifications list
10. Close the instance
11. Go to the newer instance (e.g. 12.6) and copy/cut the

    [...]webapps\xwiki

    folder and replace it (first delete the old one) in the same location on the older version

1. Start XWiki and follow DW to the end
2. Login as U1
3. Observe the notifications list

EXPECTED RESULTS

After upgrade to the new XWiki version, the user U1's notifications list displays all the events that already existed on the older version (e.g. on 11.10.5), they are preserved.

ACTUAL RESULTS

No notifications are displayed on user's notifications list.

The issue could not be reproduced when upgrading to XWiki 12.5.1 (tested upgrade from 11.10.5).