Subforum tooltip always displays "no unread posts" on viewforum.php

when forum has subforums, the tooltip for subforums on viewforum is alsways "no unread posts", whether the subforum contains unread posts or not.

the icon seems to be the correct one, depending on "unread posts" state, but the tooltip isn't.
(i left priority with default value, though i doubt this is really "major". if there was "normal" option i would change it to normal, but i am not sure "minor" or "trivial" are right for this one).

i do not have a system to test it, but the bug seems to be in

phpbb/phpBB/styles/prosilver/template/forumlist_body.html
line 48: the template tests condition "forumrow.subforum.UNREAD", but the code (functions_display.php, #531) set variable "S_UNREAD", so forumrow.subforum.UNREAD is always false.

peace.