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

this.abcCombo = new Ext.form.ComboBox({
    name : 'abcCombo',
    hiddenName : 'abcCombo-id',
    fieldLabel : "My Combobox",
    width : 250,
    editable : false,
    forceSelection : true,
    mode : 'local',
    triggerAction : 'all',
    valueField : 'id',
    displayField : 'fullName',
    store : new Ext.data.JsonStore({
       fields : ['id', 'fullName']
    }),
    tpl : '
{fullName} '

    //make sure to add this
    //if not added, empty item height is very small
    listConfig : {
        getInnerTpl: function () {
            return '
{fullName}
';
        }
    }

});

on initializing the component, you can do this (on controller):

populateMyComboBox([yourComboBoxComponent], true);

on the populate function:

populateMyComboBox : function(comboBox, insertEmpty) {
    var list;
    if (insertEmpty) {
        list.push({id : 0, fullName : ''});
    }

    var mStore = Ext.create('Ext.data.Store', {
        fields: ['data', 'label'],
        data : list.concat([real_data])
    }),

    comboBox.bindStore(mStore);
}