QGraphicsView::setMouseTracking(true) breaks QGraphicsItem::ItemIsMovable if mouse is moved outside the view

When setMouseTracking is enabled on a QGraphicsView, the item positioning is offseted if the item is dragged outside the view.

To reproduce :
1 compile attached main.cpp : qmake -project && qmake && make
2 launch mousegrab
3 left click to select the circle
4 drag it outside the view (far on the right for example)
5 bring it back inside the view (release the mouse left button)
6 re-click on the circle
7 drag the item
8 at the first movement, it gets offseted/positioned at its "old" position (the one it was at step 3)