[Confluence] smaller select dialog when button is not visible

the select dialog conditionally has a button on the right side of the list.
in cases where the button is not shown, it would leave a large empty gap.

this commit makes the dialog less wide when the button is absent.

for @da-anda



![dialog-select](https://f.cloud.github.com/assets/687265/1847618/99f8b386-765a-11e3-89a1-b687d20e6ca7.jpg)