add:  if (!document.getElementById('tb-uppity')) return;  
context: setDisabled:function(url) {	if (uppity.getURLs().length>0) {		document.getElementById('tb-uppity').removeAttribute('disabled');	} else {		document.getElementById('tb-uppity').setAttribute('disabled', true);	}},
meta: 2321	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/2321/36357b7353de82fa8e1c97e18ff8772b7a8fb99d/uppity.js/buggy/content/uppity.js