Update ucl for safe iterators.

diff --git a/src/ucl b/src/ucl
index 0823055cee510a6614fdf434d6f83ab9cad03b47..3ac2def147f73518c88f75c920a0022c27e019da 160000 (submodule)
--- a/src/ucl
+++ b/src/ucl
@@ -1 +1 @@
-Subproject commit 0823055cee510a6614fdf434d6f83ab9cad03b47
+Subproject commit 3ac2def147f73518c88f75c920a0022c27e019da