Update UTCP to fix a potential segmentation fault.

diff --git a/src/utcp b/src/utcp
index 9fe3be0ad54dd1e0c8766957ea402d555d947839..a6ea3a99259b6f74c3151d0692d2899b3657b17d 160000 (submodule)
--- a/src/utcp
+++ b/src/utcp
@@ -1 +1 @@
-Subproject commit 9fe3be0ad54dd1e0c8766957ea402d555d947839
+Subproject commit a6ea3a99259b6f74c3151d0692d2899b3657b17d