From c211268b350825f8e8f08e7c17df7601daa8a7cb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Martin=20Gr=C3=A4=C3=9Flin?= <mgraesslin@kde.org>
Date: Mon, 20 Jun 2016 17:01:15 +0200
Subject: [PATCH] Verify that windowPixmap<>() does not return a nullptr before
 accessing the children

windowPixmap() is allowed to return a nullptr, thus we need to verify
that the returned pointer is not null. If it is null it's the same as
if there are no child WindowPixmaps.
---
 scene_opengl.cpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/scene_opengl.cpp b/scene_opengl.cpp
index 38fc53ed15..239a585cc5 100644
--- a/scene_opengl.cpp
+++ b/scene_opengl.cpp
@@ -1646,7 +1646,8 @@ void SceneOpenGL2Window::performPaint(int mask, QRegion region, WindowPaintData
     setBlendEnabled(false);
 
     // render sub-surfaces
-    const auto &children = windowPixmap<OpenGLWindowPixmap>()->children();
+    auto wp = windowPixmap<OpenGLWindowPixmap>();
+    const auto &children = wp ? wp->children() : QVector<WindowPixmap*>();
     windowMatrix.translate(toplevel->clientPos().x(), toplevel->clientPos().y());
     for (auto pixmap : children) {
         if (pixmap->subSurface().isNull() || pixmap->subSurface()->surface().isNull() || !pixmap->subSurface()->surface()->isMapped()) {