--- qtdeclarative/src/quick/items/qquickwindow.cpp	Thu Nov 30 17:10:22 2017
+++ qtdeclarative/src/quick/items/qquickwindow.cpp	Wed Apr 11 21:53:11 2018
@@ -2479,6 +2479,7 @@
     bool isTouchEvent = (event->asPointerTouchEvent() != nullptr);
     for (int i = 0; i < pointCount; ++i) {
         auto point = event->point(i);
+        if (!point) continue;
         point->setAccepted(false); // because otherwise touchEventForItem will ignore it
         if (point->grabberPointerHandler() && point->state() == QQuickEventPoint::Released)
             point->setGrabberPointerHandler(nullptr, true);
@@ -2493,8 +2494,10 @@
     for (QQuickItem *item : targetItems) {
         if (!handlersOnly && sendFilteredPointerEvent(event, item)) {
             if (event->isAccepted()) {
-                for (int i = 0; i < event->pointCount(); ++i)
-                    event->point(i)->setAccepted();
+                for (int i = 0; i < event->pointCount(); ++i) {
+                    if (auto p = event->point(i))
+                        p->setAccepted();
+                }
                 return true;
             }
             skipDelivery.append(item);
@@ -2540,7 +2543,7 @@
     auto event = pointerEvent->asPointerMouseEvent();
     if (event && item->acceptedMouseButtons() & event->button()) {
             auto point = event->point(0);
-            if (point->isAccepted())
+            if (!point || point->isAccepted())
                 return;
             // The only reason to already have a mouse grabber here is
             // synthetic events - flickable sends one when setPressDelay is used.
@@ -2595,6 +2598,7 @@
         bool isPressOrRelease = pointerEvent->isPressEvent() || pointerEvent->isReleaseEvent();
         for (auto point: qAsConst(touchEvent->touchPoints())) {
             auto pointerEventPoint = ptEvent->pointById(point.id());
+            if (!pointerEventPoint) continue;
             pointerEventPoint->setAccepted();
             if (isPressOrRelease)
                 pointerEventPoint->setGrabberItem(item);
--- qtdeclarative/src/quick/items/qquickevents.cpp	Thu Nov 30 17:10:22 2017
+++ qtdeclarative/src/quick/items/qquickevents.cpp	Wed Apr 11 21:03:00 2018
@@ -1529,17 +1529,32 @@
 
 bool QQuickPointerTouchEvent::isPressEvent() const
 {
-    return static_cast<QTouchEvent*>(m_event)->touchPointStates() & Qt::TouchPointPressed;
+    QTouchEvent *touchEvent = Q_NULLPTR;
+    if (!m_event || !(touchEvent = dynamic_cast<QTouchEvent *>(m_event))) {
+        qWarning() << __FUNCTION__ << "Invalid touch event!" << m_event;
+        return false;
+    }
+    return touchEvent->touchPointStates() & Qt::TouchPointPressed;
 }
 
 bool QQuickPointerTouchEvent::isUpdateEvent() const
 {
-    return static_cast<QTouchEvent*>(m_event)->touchPointStates() & (Qt::TouchPointMoved | Qt::TouchPointStationary);
+    QTouchEvent *touchEvent = Q_NULLPTR;
+    if (!m_event || !(touchEvent = dynamic_cast<QTouchEvent *>(m_event))) {
+        qWarning() << __FUNCTION__ << "Invalid touch event!" << m_event;
+        return false;
+    }
+    return touchEvent->touchPointStates() & (Qt::TouchPointMoved | Qt::TouchPointStationary);
 }
 
 bool QQuickPointerTouchEvent::isReleaseEvent() const
 {
-    return static_cast<QTouchEvent*>(m_event)->touchPointStates() & Qt::TouchPointReleased;
+    QTouchEvent *touchEvent = Q_NULLPTR;
+    if (!m_event || !(touchEvent = dynamic_cast<QTouchEvent *>(m_event))) {
+        qWarning() << __FUNCTION__ << "Invalid touch event!" << m_event;
+        return false;
+    }
+    return touchEvent->touchPointStates() & Qt::TouchPointReleased;
 }
 
 QVector<QPointF> QQuickPointerEvent::unacceptedPressedPointScenePositions() const
--- qtdeclarative/src/quick/items/qquickevents_p_p.h	Thu Nov 30 17:10:22 2017
+++ qtdeclarative/src/quick/items/qquickevents_p_p.h	Wed Apr 11 21:42:00 2018
@@ -456,8 +456,8 @@
     bool isDoubleClickEvent() const override;
     bool isUpdateEvent() const override;
     bool isReleaseEvent() const override;
-    QQuickPointerMouseEvent *asPointerMouseEvent() override { return this; }
-    const QQuickPointerMouseEvent *asPointerMouseEvent() const override { return this; }
+    QQuickPointerMouseEvent *asPointerMouseEvent() override { return m_event && dynamic_cast<QMouseEvent *>(m_event)? this : nullptr; }
+    const QQuickPointerMouseEvent *asPointerMouseEvent() const override { return m_event && dynamic_cast<QMouseEvent *>(m_event)? this : nullptr; }
     int pointCount() const override { return 1; }
     QQuickEventPoint *point(int i) const override;
     QQuickEventPoint *pointById(int pointId) const override;
@@ -491,8 +491,8 @@
     bool isPressEvent() const override;
     bool isUpdateEvent() const override;
     bool isReleaseEvent() const override;
-    QQuickPointerTouchEvent *asPointerTouchEvent() override { return this; }
-    const QQuickPointerTouchEvent *asPointerTouchEvent() const override { return this; }
+    QQuickPointerTouchEvent *asPointerTouchEvent() override { return m_event && dynamic_cast<QTouchEvent *>(m_event)? this : nullptr; }
+    const QQuickPointerTouchEvent *asPointerTouchEvent() const override { return m_event && dynamic_cast<QTouchEvent *>(m_event)? this : nullptr; }
     int pointCount() const override { return m_pointCount; }
     QQuickEventPoint *point(int i) const override;
     QQuickEventPoint *pointById(int pointId) const override;