MessageBox Error Unable to get property 'OK' of undefined or null reference

Hi,



I've got an app where in multiple spots in the app I'm displaying a MessageBox. There are some sections of the app where I'm getting the error "Unable to get property 'OK' of undefined or null reference when I try to Show the MessageBox. The code below is one of the spots that's not working.



Code Below

editProductGroup : function() {





var grid = Ext.getCmp('headerGrid');

var arraySelected = grid.getSelectionModel().getSelection();





Ext.Ajax.request({

url : 'groupheader/getheaderstatus.action',

timeout: 720000,

method : 'POST',

params : {

groupNumber : arraySelected[0].data.groupNumber,

server : cookie.getCookie('dataSource')

},

scope : this,





success : function(response, opts) {





var responseJSON = Ext.JSON.decode(response.responseText);





if(responseJSON.success==true) {





if(responseJSON.data!='I') {

this.getProductGroupDetails(arraySelected[0].data.groupNumber);

} else {

Ext.MessageBox.show(

{

title:'Processing',

msg: 'Group is being processed cannot edit',

buttons: Ext.MessageBox.OK,

icon: Ext.MessageBox.INFO

});

}





}

}





});





},

MessageBox Error Unable to get property 'OK' of undefined or null reference