rem: !(culprit.tagName.toLowerCase() == "a" && culprit.href.match(/\.user\.js(\?|$)/i) != null); 
add: !(culprit && culprit.href.match(/\.user\.js(\?|$)/i) != null); );  
context: GM_BrowserUI.contextMenuShowing = function() {  GM_log('> contextMenuShowing');  var culprit = document.popupNode;  var contextItem = ge("install-userscript");  var contextSep = ge("install-userscript-sep");  contextItem.hidden = contextSep.hidden =     !(culprit.tagName.toLowerCase() == "a"     && culprit.href.match(/\.user\.js(\?|$)/i) != null);  GM_log('< contextMenuShowing');}
meta: 4236	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/4236/24a0ef59ca6e1fcb9ecf87cc7339f9c604378bc3/browser.js/buggy/src/content/browser.js