If finalize chardev-msmouse or chardev-wctable is called immediately after
init it cases QEMU to crash with segfault. This happens because of
QTAILQ_REMOVE in qemu_input_handler_unregister tries to dereference
NULL pointer.
For instance, this error can be reproduced via `qom-list-properties`
command.

Signed-off-by: Maksim Davydov <davydov-max@yandex-team.ru>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Message-Id: <20220825165247.33704-1-davydov-max@yandex-team.ru>