sometimes wrong inventory is shown when having multible instance in the database

I use one database for multiple instances (different worlds) and there are some players with a unique_id that have alive characters (survivors) on multiple worlds.
Sometimes I got the wrong inventory (inventory of the same player on another map) when clicking the user on the map (->admin.php?view=info&show=1&id=1234567)
The appended commit should fix the problem.