From b1a0a4c228f5adb438e44a78e5c485249cb6a89a Mon Sep 17 00:00:00 2001
From: Garret Rieger <grieger@google.com>
Date: Mon, 7 Apr 2025 18:39:21 +0000
Subject: [PATCH] In OT::VarData::Serialize don't attempt to serialize an empty
 set of rows.

Protects against incorrectly accessing rows[0] when rows is empty.
---
 src/hb-ot-layout-common.hh | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/hb-ot-layout-common.hh b/src/hb-ot-layout-common.hh
index 7b466fb0b..3c734e6a8 100644
--- a/src/hb-ot-layout-common.hh
+++ b/src/hb-ot-layout-common.hh
@@ -2863,8 +2863,13 @@ struct VarData
                   const hb_vector_t<const hb_vector_t<int>*>& rows)
   {
     TRACE_SERIALIZE (this);
-    if (unlikely (!c->extend_min (this))) return_trace (false);
     unsigned row_count = rows.length;
+    if (!row_count) {
+      // Nothing to serialize, will be empty.
+      return false;
+    }
+
+    if (unlikely (!c->extend_min (this))) return_trace (false);    
     itemCount = row_count;
 
     int min_threshold = has_long ? -65536 : -128;