Selectmenu goes of the page, how to fix?

Selectmenu goes of the page, how to fix?

Hello.

div.ui-selectmenu-menu goes of the page if Selectmenu is near the right edge of the window.


Here is the demo with some fix that I've tried:

Here is the expected behaviour:

Ie. I'm trying to align that  div.ui-selectmenu-menu on the right edge of the Selectmenu.

But for some reason I don't get expected behaviour first time when I open Selectmenu. When I close and open it againt, then it works.