When started without session related command line parameters (e.g. from
gnome-session), metacity picks up client_id from the DESKTOP_AUTOSTART_ID
environment variable. Unfortunately, there is no way to distinguish if this was
passed from a config file, representing old saved session, or generated by
gnome-session, therefore load_state is attempted in each case. If the client_id
is generated, there will be no session file, and metacity will report a
warning.
Just remove the warning so that users won't always find a warning at the
start of their .xsession-errors.
https://bugzilla.gnome.org/show_bug.cgi?id=577576