rem: if (!url.substr) { FBTrace.dumpStack("isSystemURL not a string url:"+url); return ture; } 
context: this.isSystemURL = function(url){    if (FBTrace.DBG_SHOW_SYSTEM) return false;                                                                         /*@explore*/    if (!url) return true;    if (url.length == 0) return true; // spec for about:blank    if (!url.substr)    {        FBTrace.dumpStack("isSystemURL not a string url:"+url);  // need to find why /*@explore*/        return ture;    }    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/2007/7450/5da1c8b018cf62f6e1c25d1879f31f9fb68401bb/lib.js/clean/extension/content/firebug/lib.js