Fix a crash when calling effectiveWinId() on parentless widgets.

Remove the assert as it also triggers when the widget is one
that currently has no parent (setParent(0)).
Check that the WinId is != 0 in the cursor code.

Change-Id: I711fc600f1d803c8f01c15df87984e742a4c23d2
Reviewed-by: Miikka Heikkinen <miikka.heikkinen@digia.com>
Reviewed-by: Girish Ramakrishnan <girish.1.ramakrishnan@nokia.com>

1 files changed, 5 insertions, 2 deletions

diff --git a/src/widgets/kernel/qwidget_qpa.cpp b/src/widgets/kernel/qwidget_qpa.cpp
index 355af1740e..8a6ceac526 100644
--- a/src/widgets/kernel/qwidget_qpa.cpp
+++ b/src/widgets/kernel/qwidget_qpa.cpp
@@ -989,8 +989,11 @@ void qt_qpa_set_cursor(QWidget *w, bool force)
     static QPointer<QWidget> lastUnderMouse = 0;
     if (force) {
         lastUnderMouse = w;
-    } else if (lastUnderMouse && lastUnderMouse->effectiveWinId() == w->effectiveWinId()) {
-        w = lastUnderMouse;
+    } else if (lastUnderMouse) {
+        const WId lastWinId = lastUnderMouse->effectiveWinId();
+        const WId winId = w->effectiveWinId();
+        if (lastWinId && lastWinId == winId)
+            w = lastUnderMouse;
     } else if (!w->internalWinId()) {
         return; // The mouse is not under this widget, and it's not native, so don't change it.
     }