# HG changeset patch
# User John W. Eaton <jwe@octave.org>
# Date 1426637401 14400
# Node ID ed51e17f6ccf1af6b98cf13dfb9ebd321beae2c1
# Parent  028b2302f9407720324f53f656133ff02801e66f
avoid possibly dereferencing invalid pointer

* Canvas.cc (Canvas::redraw): Check value returned from qWidget.

diff -r 028b2302f940 -r ed51e17f6ccf libgui/graphics/Canvas.cc
--- a/libgui/graphics/Canvas.cc	Tue Mar 17 21:54:53 2015 -0400
+++ b/libgui/graphics/Canvas.cc	Tue Mar 17 20:10:01 2015 -0400
@@ -45,10 +45,15 @@
 
 void Canvas::redraw (bool sync)
 {
-  if (sync)
-    qWidget ()->repaint ();
-  else
-    qWidget ()->update ();
+  QWidget *w = qWidget ();
+
+  if (w)
+    {
+      if (sync)
+        w->repaint ();
+      else
+        w->update ();
+    }
 }
 
 void Canvas::blockRedraw (bool block)