ExtJS 4 - Popup on cellclick in grid panel is not displayed - extjs

Question

I have a Problem to open a popup window on cellclick.
When i click on the cell everything overlaid grey, but the window is not displayed.
The code is in the follow. Any idea why the new Window is not displayed?
Thanks and Regards.
var win = Ext.widget('window', {
title: 'Contact Us',
closeAction: 'hide',
width: 400,
height: 400,
minHeight: 400,
layout: 'fit',
resizable: true,
modal: true,
//items: form
});
Ext.define('File',{
extend: 'Ext.data.Model',
fields: [
{name: 'file_id'},
{name: 'file_input_filename'},
{name: 'file_type'},
{name: 'lc_status'},
{name: 'file_input_date'}
]
});
// create the Data Store
var overviewStore = Ext.create('Ext.data.Store', {
model: 'File',
autoLoad: true,
proxy: {
type: 'ajax',
url: 'FileOverview',
reader: {
type: 'xml',
// records will have an "Item" tag
record: 'Row',
idProperty: 'file_id',
totalRecords: '#total'
}
}
});
// create the grid
var gridOverview = Ext.create('Ext.grid.Panel', {
store: overviewStore,
id: 'OverviewGridPanelId',
columns: [
{text: "ID", flex: 1, dataIndex: 'file_id', sortable: true},
{text: "Filename", width: 180, dataIndex: 'file_input_filename', sortable: true},
{text: "Filetyp", width: 180, dataIndex: 'file_type', sortable: true},
{text: "Status", width: 180, dataIndex: 'lc_status', sortable: true},
{text: "Imported", width: 115, dataIndex: 'file_input_date', sortable: true}
],
renderTo:'binding-example',
width: 1200,
height: 650,
});
gridOverview.on('cellclick', function(table, td, cellIndex, record, tr, rowIndex, e, eOpts) {
var masterIndex = rowIndex;
//openDialog(record.get('file_id'));
Ext.Msg.alert('locked grid click');
win.show();
});
}