Setting position causes "TypeError: Cannot read property 'length' of undefined".

[duckmaestro]

The following simple code causes a type error while executing the last line (.position = ...):

        var canvas = document.getElementById("mainCanvas");                
        paper.setup(canvas);

        var inspector = new paper.Group();
        var clip = paper.Shape.Rectangle(new paper.Point(0, 0), new paper.Size(200, 200));
        inspector.addChild(clip);
        clip.clipMask = true;

        var background = paper.Shape.Rectangle(new paper.Point(0, 0), new paper.Size(200, 200));
        inspector.addChild(background);
        background.fillColor = new paper.Color(1, 1, 1, 1);
        background.strokeColor = new paper.Color(0.5, 0.5, 0.5, 1);
        background.strokeWidth = 1;

        inspector.position = new paper.Point(300, 300);

I've tried both v0.9.8 as well as the latest nightly (v0.9.9), and have tried both Chrome and Awesomium. I've also tried new paper.Shape.Rectangle(...) instead of just paper.Shape.Rectangle(...).

The call stack (on v0.9.8) that I get is:

TypeError: Cannot read property 'length' of undefined
    at Shape.Base.extend.isEmpty (paper.js:2790:24)
    at Group.Base.extend.Base.each._getBounds (paper.js:2857:33)
    at Group.Base.extend.Base.each._getCachedBounds (paper.js:2825:21)
    at Group.Base.extend.Base.each.(anonymous function) (paper.js:2796:19)
    at Group.Base.extend.getPosition (paper.js:2771:31)
    at Group.Base.extend.setPosition (paper.js:2777:54)
    at window.onload (index2.html:94:36)