fix build of timing.c
diff --git a/demo/timing.c b/demo/timing.c
index 1a5a05b..f620b8c 100644
--- a/demo/timing.c
+++ b/demo/timing.c
@@ -26,7 +26,7 @@ static void ndraw(mp_int *a, const char *name)
char buf[4096];
printf("%s: ", name);
- mp_to_radix(a, buf, sizeof(buf), 64);
+ mp_to_radix(a, buf, sizeof(buf), NULL, 64);
printf("%s\n", buf);
}