Roman Lebedev authored Aug 22, 2023 and Wim Taymans committed Aug 23, 2023

It is sometimes useful to add a custom profile-set.
For that, e.g. `default.conf` needs to be modified.
(at least, i have not succeeded in just adding a new file)

But that change gets overridden when the package is updated,
which could be *extremely* dangerous, e.g. if said profile
changed the `volume-limit`.

By shipping an "empty" `9999-custom.conf`,
the update becomes less problematic,
because one can now use e.g. `dpkg-divert` on said file.

Refs. https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1050293