Assignment to list property yields unexpected result

import QtQuick 1.0

Item {
    id: root
    width: 640
    height: 480

    property list<Rectangle> rects: [
        Rectangle { width: 100; height: 100 },
        Rectangle { width: 200; height: 100 },
        Rectangle { width: 300; height: 100 },
        Rectangle { width: 400; height: 100 }
    ]

    Item {
        id: item
        property list<Rectangle> theRects
        onTheRectsChanged: {
            print("New list length: " + theRects.length);
            if(theRects.length > 0)
                print("Last item's width: " + theRects[theRects.length-1].width);

        }
    }

    MouseArea {
        anchors.fill: parent
        onClicked: item.theRects = root.rects
    }
}

New list length: 4
Last item's width: 400

New list length: 0
New list length: 1
file:///home/mathias/dev/gitorious/mathiasm-qt-components/tools/StretchBench.qml:23: TypeError: Result of expression 'theRects[theRects.length-1]' [null] is not an object.