Crash when adding a layout with a parent layout item to another layout.

The crash seems to be triggered by the following line:
QGraphicsGridLayout *innerLayout = new QGraphicsGridLayout(widget);

You don't have to pass the widget pointer here, (it will be reparented anyway). Changing that line to

QGraphicsGridLayout *innerLayout = new QGraphicsGridLayout;

will make the crash go away. This is recommended to do regardless of the resolution of this bug.