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The tally of which stocks you already own breaks down if you own any stocks worth 0, presumably because these don't appear in the master list. Adding this after line 95 (if (thisLink.href.match('ticker=')){) fixes it by skipping those:

var worth = thisLink.parentNode.parentNode.getElementsByTagName('td')[3].innerHTML;
if (worth == 0) {
// worthless stocks don't appear in the big list
continue;
}