From 0232bcdfa4e685689ff883023018989fd76d45e8 Mon Sep 17 00:00:00 2001
From: FranklinDM <mrmineshafter17@gmail.com>
Date: Sat, 18 Mar 2023 12:44:56 +0800
Subject: [PATCH] Issue #1592 - Part 1a: Prevent crashing if a slot element was
 selected via DOM Inspector

---
 layout/base/RestyleManager.cpp | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/layout/base/RestyleManager.cpp b/layout/base/RestyleManager.cpp
index 9e80ef7bc7..da9b47ece9 100644
--- a/layout/base/RestyleManager.cpp
+++ b/layout/base/RestyleManager.cpp
@@ -3839,8 +3839,13 @@ RestyleManager::ComputeAndProcessStyleChange(nsStyleContext*        aNewContext,
   MOZ_ASSERT(mReframingStyleContexts, "should have rsc");
   MOZ_ASSERT(aNewContext->StyleDisplay()->mDisplay == StyleDisplay::Contents);
   nsIFrame* frame = GetNearestAncestorFrame(aElement);
-  MOZ_ASSERT(frame, "display:contents node in map although it's a "
-                    "display:none descendant?");
+  // Return early if we don't have a frame.
+  if (!frame) {
+    NS_ASSERTION(frame,
+                 "display:contents node in map although it's a "
+                 "display:none descendant?");
+    return;
+  }
   TreeMatchContext treeMatchContext(true,
                                     nsRuleWalker::eRelevantLinkUnvisited,
                                     frame->PresContext()->Document());