From a94a663200b6c14d6b5404f6cef4be94b4d8d13b Mon Sep 17 00:00:00 2001
From: David Bolter <dbolter@mozilla.com>
Date: Tue, 10 Jan 2012 13:52:14 -0500
Subject: [PATCH] Bug 716589 - crash nsDocAccessible::GetNativeWindow.
 r=tbsaunde

---
 accessible/src/base/nsDocAccessible.cpp | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/accessible/src/base/nsDocAccessible.cpp b/accessible/src/base/nsDocAccessible.cpp
index f4d8bcf56929..7516bac7e0a8 100644
--- a/accessible/src/base/nsDocAccessible.cpp
+++ b/accessible/src/base/nsDocAccessible.cpp
@@ -1278,13 +1278,18 @@ void*
 nsDocAccessible::GetNativeWindow() const
 {
   nsCOMPtr<nsIPresShell> shell(do_QueryReferent(mWeakShell));
+  if (!shell)
+    return nsnull;
+
   nsIViewManager* vm = shell->GetViewManager();
-  if (vm) {
-    nsCOMPtr<nsIWidget> widget;
-    vm->GetRootWidget(getter_AddRefs(widget));
-    if (widget)
-      return widget->GetNativeData(NS_NATIVE_WINDOW);
-  }
+  if (!vm)
+    return nsnull;
+
+  nsCOMPtr<nsIWidget> widget;
+  vm->GetRootWidget(getter_AddRefs(widget));
+  if (widget)
+    return widget->GetNativeData(NS_NATIVE_WINDOW);
+
   return nsnull;
 }