Unrecognised selector sent to instance in fire event?

hi i am using raphael charts to draw and i send fire event first time it work next time it give error

error is

  -[TiUILabelProxy fireEvent:withObject:remove:thisObject:]: unrecognized selector sent to instance

my code is

          var webview = Titanium.UI.createWebView({
          width: Ti.UI.FILL,
          height: 240,
          url: '/Chart/chart.html',
          borderColor:"#efefef",
      borderWidth:1,
      enableZoomControls:false
        });

     view.add(webview);
        webview.addEventListener("load",function(){           
                 Ti.App.fireEvent('renderChart',ChartData); 

            });

and my chart.html code is

        <script>
        Ti.App.addEventListener('renderChart', function(chartData) {
                    Ti.API.info('The renderChart event happened');
            //some code
        }
    </script>

it produce error in ios how to solve that