From d53d6f3bcefc3e7f42cdf4920d24dc851aa63b00 Mon Sep 17 00:00:00 2001
From: Albrecht Schlosser <albrechts.fltk@online.de>
Date: Wed, 10 Feb 2021 14:11:04 +0100
Subject: Fix potential NULL pointer dereference

---
 src/Fl_Window.cxx | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Fl_Window.cxx b/src/Fl_Window.cxx
index f489fe89a..26e259b5d 100644
--- a/src/Fl_Window.cxx
+++ b/src/Fl_Window.cxx
@@ -135,7 +135,7 @@ Fl_Window* Fl_Widget::top_window_offset(int& xoff, int& yoff) const {
     yoff += w->y();
     w = w->window();                    // walk up window hierarchy
   }
-  return const_cast<Fl_Widget*>(w)->as_window();
+  return w ? const_cast<Fl_Widget*>(w)->as_window() : NULL;
 }
 
 /** Gets the x position of the window on the screen */
-- 
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