Button alignment issue at window's tabs

I have a problem when I try to align buttons created in HTML and these buttons are within a tab, which in turn is within a window

Snippet http://codepaste.net/e81poo

so i tried to align them using a div with fillspace property= true, but this only works at the first tab, then i used a div with a fixed width, but i really dont like this technique

According to the Webix rules of sizing and positioning, an empty layout will fill all available space, so you don’t need to use the fixed width for it.

For example: http://webix.com/snippet/b215ea05

Also, there’s a gravity property, which allows setting the relative size to the components.

If the mentioned approach doesn’t help, we will appreciate a live demo that will demonstrate the issue.