From cb05fe0f70039077bdc1c72f0e2121be6eb7835b Mon Sep 17 00:00:00 2001
From: Eddie Hung <eddie@fpgeh.com>
Date: Wed, 27 Nov 2019 00:51:39 -0800
Subject: [PATCH] Check for nullptr

---
 passes/hierarchy/submod.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/passes/hierarchy/submod.cc b/passes/hierarchy/submod.cc
index 349483778..7b5e110cb 100644
--- a/passes/hierarchy/submod.cc
+++ b/passes/hierarchy/submod.cc
@@ -141,7 +141,7 @@ struct SubmodWorker
 			else {
 				auto sig = sigmap(wire);
 				for (auto c : sig.chunks())
-					if (c.wire->port_output) {
+					if (c.wire && c.wire->port_output) {
 						flags.is_ext_used = true;
 						break;
 					}