add: if(!fbs) return; 
context:     onScriptDestroyed: function(script)    {		var scriptTag = script.tag;		if (fbs.DBG_CREATION) ddd("onScriptDestroyed tag:"+scriptTag+"\n"+getStackDump()+"\n");                        /*@explore*/			        if (scriptTag in this.scriptInfoByTag)          {        	var scriptInfo = this.scriptInfoByTag[scriptTag]; 			var url = scriptInfo.url;			if (url in this.scriptInfoArrayByURL)        		remove(this.scriptInfoArrayByURL[url], scriptInfo);        	delete this.scriptInfoByTag[scriptTag];        }    		delete this.nestedScriptStack[scriptTag];        delete this.eventLevelScriptTag[scriptTag];		// XXXms: verify this        //if (url && !isSystemURL(url))        //    dispatch(scriptListeners,"onScriptDestroyed",[script]);    },
meta: 7450	/local1/tlutelli/issta_data/temp/all_js/javascript/2007_temp/2007/7450/c4cde785872f9564974cbcb5f51250cbf9e542db/firebug-service.js/buggy/extension/components/firebug-service.js