Why am I getting this error "ct is null" error. Can anyone help me. I have button in north region on click trying to display formpanel in south thats it.

Code:
..
var ADD= function(record){
    
    var add= new Ext.FormPanel({
        id: 'addcase',
        items: [{
            xtype: 'textfield',
            fieldLabel: 'Name',
            name: 'targetName'
        }]
...
    })
    ADD.render(record);
}
..
...
         xtype:'tbbutton',
         text:'Display Form',
         handler: ADD
....