rem: if (url.length == 0) return false; 
add: if (url.length == 0) return true; 
context: this.isSystemURL = function(url){    if (FBTrace.DBG_SHOW_SYSTEM) return false;                                                                         /*@explore*/    if (!url) return true;    if (url.length == 0) return false; // spec for about:blank    if (url.substr(0, 9) == "resource:")        return true;    else if (url.substr(0, 17) == "chrome://firebug/")        return true;    else if (url.substr(0, 6) == "about:")        return true;    else if (url.indexOf("firebug-service.js") != -1)        return true;    else        return false;};
meta: 7450	/local1/tlutelli/issta_data/temp/all_js/javascript/2007_temp/2007/7450/996ee4011c3ce2b20b53838d2657530af68e3e49/lib.js/clean/extension/content/firebug/lib.js