Lightbox doesn't always find the correct page height in Opera

The following work-around works for me, and should make it easier to fix the problem:

var Lightbox = Lightbox || {};

Lightbox.oldGetPageSize = Lightbox.getPageSize;

Lightbox.getPageSize = function() {
  var pageSizes = Lightbox.oldGetPageSize();
  pageSizes[1] = Math.max(
    Math.max(document.body.scrollHeight, document.documentElement.scrollHeight),
    Math.max(document.body.offsetHeight, document.documentElement.offsetHeight),
    Math.max(document.body.clientHeight, document.documentElement.clientHeight)
  );
  return pageSizes;
}