From fc8693795b892b2077beab30b91ee5d2590ad7c0 Mon Sep 17 00:00:00 2001
From: Tetsuharu OHZEKI <tetsuharu.ohzeki@gmail.com>
Date: Sun, 2 Feb 2020 17:02:38 +0000
Subject: [PATCH] Bug 1597478 - follow up: add the null check for
 `mPresContext`. r=emilio

Differential Revision: https://phabricator.services.mozilla.com/D61416

--HG--
extra : moz-landing-system : lando
---
 layout/base/nsDocumentViewer.cpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/layout/base/nsDocumentViewer.cpp b/layout/base/nsDocumentViewer.cpp
index e725c2fb3a1b..6dcd47ebad30 100644
--- a/layout/base/nsDocumentViewer.cpp
+++ b/layout/base/nsDocumentViewer.cpp
@@ -3871,6 +3871,9 @@ bool nsDocumentViewer::ShouldAttachToTopLevel() {
 
 #if defined(XP_WIN) || defined(MOZ_WIDGET_GTK) || \
     defined(MOZ_WIDGET_ANDROID) || defined(MOZ_WIDGET_UIKIT)
+  if (!mPresContext) {
+    return false;
+  }
 
   // On windows, in the parent process we also attach, but just to
   // chrome items