Platform preferences do not update on newer KDE systems

[Christopher Schnick]

I have the problem on 2 separate KDE systems now where the Platform 
preferences map is not updated at runtime on KDE. The values on startup 
seem to be correct though.

My main testing system is a Debian 13 forky/sid testing system with KDE 
version 6.5.3 from |plasmashell -v.|