Check for existence of QWindow in QApplication::isBlockedByModal.

Warn if window == 0 is passed in
QApplicationPrivate::isWindowBlocked().

Task-number: QTBUG-28637
Change-Id: I1213ea371813eeb90f962cc39235ddfccc663d45
Reviewed-by: Jing Bai <jing.bai@digia.com>
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/src/widgets/kernel/qapplication.cpp b/src/widgets/kernel/qapplication.cpp
index ed6262ce93..c66a4487b4 100644
--- a/src/widgets/kernel/qapplication.cpp
+++ b/src/widgets/kernel/qapplication.cpp
@@ -2217,12 +2217,17 @@ Q_WIDGETS_EXPORT bool qt_tryModalHelper(QWidget *widget, QWidget **rettop)
 bool QApplicationPrivate::isBlockedByModal(QWidget *widget)
 {
     widget = widget->window();
-    return self->isWindowBlocked(widget->windowHandle());
+    QWindow *window = widget->windowHandle();
+    return window && self->isWindowBlocked(window);
 }
 
 bool QApplicationPrivate::isWindowBlocked(QWindow *window, QWindow **blockingWindow) const
 {
     QWindow *unused = 0;
+    if (!window) {
+        qWarning().nospace() << "window == 0 passed.";
+        return false;
+    }
     if (!blockingWindow)
         blockingWindow = &unused;