desktop-shell: Initialise panel surface listener

The desktop-shell output destroy code assumes that we always set up a
panel listener. Initialise its list explicitly, so if we don't have a
panel, then we can still unconditionally destroy the listener on output
destroy.

Signed-off-by: Daniel Stone <daniels@collabora.com>
Reviewed-by: Quentin Glidic <sardemff7+git@sardemff7.net>
1 file changed