Steps to reproduce

(1) -Access your Users/Editors user group
(2) -Verify that no user is created in that group
(3) -Create one user
(4) -Right after the creation, view the "Editors" group. The sub-items list continues to display Sub-items(0)
(5) -If we clear caches, then the user can be seem and sub-items list count is correct.

Note1: Having already one user created, any additional user's will appear on sub-items list without the need of clearing caches.

Note2: Also, when we delete users, the sub-items count list isn't updated.

Note3: This behaviour doesn't happen with other objects (folders, articles, etc)

We already have had more or less the same issue in EZP-25003, but for other objects. This was solved, but apparently not completely in the users case.