object_property_add_alias() is called at some
places at present. And its parameter errp may not NULL,
such as
 object_property_add_alias(obj, "iothread", OBJECT(&dev->vdev),"iothread",
                              &error_abort);
This patch add error handler for security.

Cc: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Markus Armbruster <armbru@redhat.com>
Reviewed-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NGonglei <arei.gonglei@huawei.com>
Signed-off-by: NAndreas Färber <afaerber@suse.de>