From 21daa1d5cbd2fb2b701426d0ba3f6a081a8f81ad Mon Sep 17 00:00:00 2001
From: wolfbeast <mcwerewolf@wolfbeast.com>
Date: Mon, 18 Feb 2019 22:24:29 +0100
Subject: [PATCH] Add nullcheck for frames in FindNearestCommonAncestorFrame

This resolves #978.
---
 layout/base/nsLayoutUtils.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/layout/base/nsLayoutUtils.cpp b/layout/base/nsLayoutUtils.cpp
index f0341f9eff..07befdc812 100644
--- a/layout/base/nsLayoutUtils.cpp
+++ b/layout/base/nsLayoutUtils.cpp
@@ -2681,6 +2681,10 @@ nsLayoutUtils::GetTransformToAncestorScaleExcludingAnimated(nsIFrame* aFrame)
 nsIFrame*
 nsLayoutUtils::FindNearestCommonAncestorFrame(nsIFrame* aFrame1, nsIFrame* aFrame2)
 {
+  if (!aFrame1 || !aFrame2) {
+    return nullptr;
+  }
+
   AutoTArray<nsIFrame*,100> ancestors1;
   AutoTArray<nsIFrame*,100> ancestors2;
   nsIFrame* commonAncestor = nullptr;