I discovered the following issue while trying to use the "Notification settings" page in the "Site administration" area:
The title of the issue should give you the idea about the nature of the problem, but in it I supplised more information about it.
As I wrote inside this issue in Moodle Tracker website, DO TRY TO REPRODUCE THIS SCENARIO ON A PRODUCTION ENVIRONMENT, OR EVEN A TEST ENVIRONMENT THAT YOU CAN'T RECOVER QUICKLY AND EASILY FROM A BACKUP, SINCE .
I just want to bring this issue to the attention of people, so they wouldn't be affected by it while trying to do a simple action in the system.
If I'm missing something or if you can shed some light about this issue, that would be great.