[LyX/master] Zoom slider

[Pavel Sanda]

On Sun, Mar 07, 2021 at 01:24:29PM +0100, Juergen Spitzmueller wrote:
> commit bdb006543b43f71a06fc5b9915d0df19aae0ef68
> Author: Juergen Spitzmueller <spitz at lyx.org>
> Date:   Sun Mar 7 13:29:23 2021 +0100
> 
>     Zoom slider

Juergen, would you mind if slider and its buttons were toggling between
visible/invisible rather than enabled/disabled?
It would look imho better when no document is loaded.

Pavel