From 2b88d79adc3aa59f9bdd33c276303fbfdac777fa Mon Sep 17 00:00:00 2001
From: Tim Edwards <tim@opencircuitdesign.com>
Date: Fri, 16 Aug 2024 19:48:36 -0400
Subject: [PATCH] Corrected a rare case where a NULL value propagates in the
 flattening routine and is not caught until it causes a segfault.

---
 VERSION        | 2 +-
 base/flatten.c | 6 ++++--
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/VERSION b/VERSION
index b6bd287..c6531a7 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-1.5.276
+1.5.277
diff --git a/base/flatten.c b/base/flatten.c
index 78596e4..f9840b7 100644
--- a/base/flatten.c
+++ b/base/flatten.c
@@ -600,8 +600,10 @@ int flattenInstancesOf(char *name, int fnum, char *instance)
          else break;
 
          /* Put the child cell at the start of ChildObjList */
-         ChildEnd->next = ChildObjList;
-         ChildObjList = ChildStart;
+	 if (ChildEnd) {
+            ChildEnd->next = ChildObjList;
+            ChildObjList = ChildStart;
+	 }
       }
 
       /* Put the child cell at the start of ChildObjList */