add: if (!status) return; 
context:         _update: function(status) {            if (status.sent) {                if (status.finished) {                    this.barNode.style.width = "100%";                    this._timer.stop();                } else {                    this.barNode.style.width = status.percent + "%";                }                           }            if (status.message) this.msgNode.innerHTML = status.message;        },
meta: 1201	/local1/tlutelli/issta_data/temp/all_js/javascript/2007_temp/2007/1201/7826366b3d926533ef8980e82c454cc60331de48/FormUploadProgress.js/clean/blocks/cocoon-ajax/cocoon-ajax-impl/src/main/resources/org/apache/cocoon/ajax/resources/js/FormUploadProgress.js