Application crashes on selecting an item in RadSide Drawer

Hi,

I am using a RadSideDrawer as shown in this link (http://docs.telerik.com/devtools/xamarin/controls/sidedrawer/sidedrawer-overview).

I have a Grouped listview to show hierarchical data. When I select an item from side drawer for the first time, it alerts correct information, but if I try to select second item it crashes. 

Is there any working sample on Side Drawer, can someone help me with this?

       private void M4ReportDrawer_SelectionChanged(object sender, NotifyCollectionChangedEventArgs e)
        {
            object cc = e.NewItems[0];
            string reportName =  (cc as M4DrawerItem).ReportName;
             this.DisplayAlert("Selected item:", reportName, "OK");
            (this.Content.FindByName<RadSideDrawer>("M4ReportDrawer")).IsOpen = false;
        }

Regards,

Prava