From 2be0261d545c84a2886ef31b573f92c9573e59f2 Mon Sep 17 00:00:00 2001
From: FranklinDM <mrmineshafter17@gmail.com>
Date: Sat, 11 Mar 2023 12:08:20 +0800
Subject: [PATCH] Issue #2078 - Follow-up: Ensure empty selector lists aren't
 iterated when serialized

Really odd that this wasn't caught/doesn't cause any issues on MSVC/unoptimized GCC. Must've been luck, I guess.
---
 layout/style/StyleRule.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/layout/style/StyleRule.cpp b/layout/style/StyleRule.cpp
index f4a3d05e5b..0ae939098a 100644
--- a/layout/style/StyleRule.cpp
+++ b/layout/style/StyleRule.cpp
@@ -1048,6 +1048,10 @@ nsCSSSelectorList::ToString(nsAString& aResult, CSSStyleSheet* aSheet)
 {
   aResult.Truncate();
   nsCSSSelectorList *p = this;
+  // Don't append anything if we're an empty selector list.
+  if (!mSelectors) {
+    return;
+  }
   for (;;) {
     p->mSelectors->ToString(aResult, aSheet, true);
     p = p->mNext;