How to add an empty item to ExtJS combobox?

Question

I want to add and empty item (display value is blank, item height is kept as normal) to an Ext.form.ComboBox. I refered 2 links below to configure my combobox, but it still

Answer 1

You can add an "empty" record at the beginning:

 listeners: {
     load: function(store, records) {
          store.insert(0, [{
              fullName: ' ',
              id: null
          }]);
     }
  }