:art: Optionnal None in unions

diff --git a/ast b/ast
index df2bc1f376c00d733304f1ea7f3c5ed6f76b84de..0fc6ac705674b97d2edb4c60ec225d8e840dfc3f 160000 (submodule)
--- a/ast
+++ b/ast
@@ -1 +1 @@
-Subproject commit df2bc1f376c00d733304f1ea7f3c5ed6f76b84de
+Subproject commit 0fc6ac705674b97d2edb4c60ec225d8e840dfc3f