From b29522749a9ba7245485766d0101c700847a11b6 Mon Sep 17 00:00:00 2001
From: FranklinDM <mrmineshafter17@gmail.com>
Date: Wed, 22 Mar 2023 17:29:00 +0800
Subject: [PATCH] Issue #1592 - Follow-up: Don't post a restyle event if
 restyleElement is null

This fixes a potential crash caused if restyleElement is null.
---
 dom/base/ShadowRoot.cpp | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/dom/base/ShadowRoot.cpp b/dom/base/ShadowRoot.cpp
index 8482da5e99..abf6301123 100644
--- a/dom/base/ShadowRoot.cpp
+++ b/dom/base/ShadowRoot.cpp
@@ -163,6 +163,7 @@ ShadowRoot::AddSlot(HTMLSlotElement* aSlot)
 
       oldSlot->RemoveAssignedNode(assignedNode);
       currentSlot->AppendAssignedNode(assignedNode);
+
       Element* restyleElement;
       if (assignedNode->IsElement()) {
         restyleElement = assignedNode->AsElement();
@@ -170,8 +171,10 @@ ShadowRoot::AddSlot(HTMLSlotElement* aSlot)
         // This is likely a text node. Use the host instead.
         restyleElement = GetHost();
       }
-      nsLayoutUtils::PostRestyleEvent(
-        restyleElement, eRestyle_Subtree, nsChangeHint(0));
+      if (restyleElement) {
+        nsLayoutUtils::PostRestyleEvent(
+          restyleElement, eRestyle_Subtree, nsChangeHint(0));
+      }
 
       doEnqueueSlotChange = true;
     }