From ef906c715e032f8a631813048947611cca788cec Mon Sep 17 00:00:00 2001
From: Moonchild <moonchild@palemoon.org>
Date: Tue, 26 Jan 2021 09:56:37 +0000
Subject: [PATCH] [layout, XUL] Avoid accessing invalidated frame.

---
 layout/xul/tree/nsTreeBodyFrame.cpp | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/layout/xul/tree/nsTreeBodyFrame.cpp b/layout/xul/tree/nsTreeBodyFrame.cpp
index b31d1de367..ec054a234e 100644
--- a/layout/xul/tree/nsTreeBodyFrame.cpp
+++ b/layout/xul/tree/nsTreeBodyFrame.cpp
@@ -1826,12 +1826,17 @@ nsTreeBodyFrame::RowCountChanged(int32_t aIndex, int32_t aCount)
     FireRowCountChangedEvent(aIndex, aCount);
 #endif
 
+  nsWeakFrame weakFrame(this);
+  
   // Adjust our selection.
+  nsCOMPtr<nsITreeView> view = mView;
   nsCOMPtr<nsITreeSelection> sel;
-  mView->GetSelection(getter_AddRefs(sel));
+  view->GetSelection(getter_AddRefs(sel));
   if (sel)
     sel->AdjustSelection(aIndex, aCount);
 
+  NS_ENSURE_STATE (weakFrame.IsAlive());
+  
   if (mUpdateBatchNest)
     return NS_OK;