getBBox() bug in Firefox

HTML

<svg>
    <g id="visible"><rect />
        <rect fill="#000" width="100" height="100"></rect>
    </g>
    <g id="hidden" display="none">
        <rect fill="#f00" width="100" height="100"></rect>
    </g>
</svg>

JavaScript

var w;

w = document.getElementById('visible').getBBox().width;
alert('visible: ' + w);


// Chrome reports 0.
// Firefox dies with a DOM exception.
// NS_ERROR_FAILURE: Component returned failure code: 0x80004005 (NS_ERROR_FAILURE) [nsIDOMSVGLocatable.getBBox]

w = document.getElementById('hidden').getBBox().width;
y=document.getElementById("hidden").getAttribute("name")
alert('hidden: ' + w);
alert('hidden: ' + y);