make lpi_fini handle NULL to allow it after failed lpi_init in ud_open

https://github.com/xemul/criu/issues/187Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

criu/uffd.c

@@ -76,6 +76,8 @@ static struct lazy_pages_info *lpi_init(void)
 
 static void lpi_fini(struct lazy_pages_info *lpi)
 {
+	if (!lpi)
+		return;
 	if (lpi->uffd > 0)
 		close(lpi->uffd);
 	if (lpi->pr.close)