Tablet event delivered to wrong widget after doing DnD on X11

When starting a simple DnD (e.g. from an item view) using a tablet device (WACOM Cintiq 21UX) which has a pixmap assigned, the tablet release event isn't properly delivered to QETWidget::handleXInputEvent.
It is important that the pixmap's pixel right under the cursor is NOT transparent (thus the internally used QShapedPixmapWidget will receive events).

While this was a not so big issue in Qt versions prior to 4.6 (the application simply missed a tablet release event) the change a2b2fbbbffa4fa04f47cd8b9e6265e2e61c5e5f3 introduced the unwanted feature that the next tablet events are being delivered to the widget the drag was started from - no matter where the user clicked this time.

Since we're developing an application where the user can drag things from itemviews onto a working canvas where one can manipulate things using tablet-aware code this bug requires to click once into the right widget before tablet events are delivered right.

Note that clearing the widgetToGetPress member when receiving the TabletLeaveProximity event would fix this issue in our setup.