To reproduce, follow the instructions in the Moodle docs to disable the 'Private files' repository and remove the capability to view/manage own files from all roles.

Note that when logged in as an admin user, the link to 'My private files' still appears in the navigation block under 'My profile' and user is still able to use that functionality.

In MDL-25651, it seems that the intention was to check that the repository was enabled before adding to the navigation but it was never implemented as such.