fullscreen-shell: Avoid NULL pointer dereference

When there are no outputs present, an output pointer
can be NULL. Dereferencing such pointer will result
in a crash.

Signed-off-by: Armin Krezović <krezovic.armin@gmail.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
1 file changed