Zero-initialize paint-device in minimal EGL platform plugin

Change-Id: Ic6b39825cf349f8ad8a56b1fb5dd3855f8675519
Reviewed-by: Morten Johan Sørvig <morten.sorvig@digia.com>
Reviewed-by: Samuel Rødal <samuel.rodal@digia.com>
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@digia.com>

src/plugins/platforms/minimalegl/qminimaleglbackingstore.cpp

@@ -49,6 +49,7 @@ QT_BEGIN_NAMESPACE
 QMinimalEglBackingStore::QMinimalEglBackingStore(QWindow *window)
     : QPlatformBackingStore(window)
     , m_context(new QOpenGLContext)
+    , m_device(0)
 {
     m_context->setFormat(window->requestedFormat());
     m_context->setScreen(window->screen());