strange behaviour in .refresh() ..

Dear madams/sirs,

I found a very strange behaviour that when I to update a form label and combo options , the code I show below:

if I swap line 1 and 2, the refresh() call shows "undefined … " in each option,
but in the order ,works well, how does this happen ? My curiosity.

  1 )$$('jobcost').define('options','4.0,4.3,4.6,4.9'.split(','));
  2 )  $$('jobcost').define('label','時薪');
  3 )  $$('jobcost').refresh();

It works correctly for me.
Please check http://webix.com/snippet/0b4ef285