Long buttons in modal-footer don't start on a new line

Created by: anatolebeuzon

It looks like there is an issue with buttons when they are used in a modal-footer. If they are too long, they do not start on a new line like it would be expected. Instead, they appear to be out of their container:

The reduced case is pretty straightforward, simply copying and pasting the code snippet from the docs reproduces it.

(For the sake of the example, the buttons have very long text, but the bug is also observable with reasonably short button text on small displays such as iPhone 5).

I could observe this behaviour with Safari (mobile & desktop) and Chrome (desktop), so I suppose it is not browser-specific.