Permissions assigned to a user are added or rendered twice

When creating a user and assigning access to a language and client, and setting permissions to areas, the permissions will be defined and/or rendered twice.

This behaviour can be seen in the overviews of area, content and category permissions for groups and users.

See related topic in forum:
https://forum.contenido.org/viewtopic.php?f=98&t=43469#p179499