event.blind.js effect will trigger script error in IE7

I've tracked down the problem to the following lines of code within the effect.core.js script

The following lines within the createWrapper function will produce under certain circumstances NaN values for top & left.

var top = parseInt(el.css('top'), 10); if (top.constructor != Number) top = 'auto';
var left = parseInt(el.css('left'), 10); if (left.constructor != Number) left = 'auto';

fix:

var top = parseInt(el.css('top'), 10); if (isNaN(top)) top = 'auto';
var left = parseInt(el.css('left'), 10); if (isNaN(left)) left = 'auto';