Empty line in ComboBox

[zilav]

Apparently ExtJS can't display empty lines in dropdown list of ComboBox.

I used this code in MainForm.Script for ExtJS 3 to fix it:

Ext.override(Ext.form.ComboBox, {
  initList: (function(){
    if(!this.tpl) {
      this.tpl = new Ext.XTemplate('<tpl for="."><div class="x-combo-list-item">{', this.displayField , ':this.blank}</div></tpl>', {
        blank: function(value){
         return value==='' ? '&nbsp' : value;
        }
      });
    }
  }).createSequence(Ext.form.ComboBox.prototype.initList)
});

I searched for similar global in ExtJS 4 and found this article

http://ahlearns.wordpress.com/2013/06/20/ext-js-4-empty-value-in-a-combobox/

 

Unfortunately it doesn't work for me.

Does anyone know why not working, or another possible solution to fix all ComboBoxes?

Would like to see this in UniGUI by default.