processes: Gracefully handle daemons without clients.

Fixes <https://bugs.gnu.org/34716>.
Reported by Mark H Weaver <mhw@netris.org>.

The problem could be reproduced by running, on one hand:

  sh -c 'exec -a guix-daemon sleep 777'

and on the other hand:

  guix processes

If there is no process with PID 777, 'guix processes' would barf as it
stumbles upon a <daemon-session> record whose client is #f.

* guix/scripts/processes.scm (daemon-sessions)[child-process->session]:
New procedure, with lambda formerly passed to 'map'.  Handle #f returns
from 'lookup-process'.
Call 'child-process->session' within 'filter-map', not just 'map'.

0 files changed, 0 insertions, 0 deletions