Dynamic form fields : cloning fields and fieldsets on the fly

[rsgjenny09]

Try to delete a fieldset by clicking on the minus icon, receive recusive 'this.dom is undefined' message. Tried 'Ext.layout.FormLayout.prototype.trackLabels = true;', same error. Did anyone try with Ext 3.2?
No validation apply yet.

Code as below:
xtype: 'fieldset'
,nameSpace: 'splitform'
,maxOccurs: 5
,dynamic: true
,items: [{
xtype: 'numberfield'
,name: 'start'
,fieldLabel: 'Start'
},{
xtype: 'numberfield'
,name: 'end'
,fieldLabel: 'End'

}]