Check for nullptr

diff --git a/passes/hierarchy/submod.cc b/passes/hierarchy/submod.cc
index 3494837789ee1a863fb952d62f6b604ccb6681c8..7b5e110cb3715f3dd0a8f075318e314cd6a78e09 100644 (file)
--- 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;
                                        }