bug#20813: 25.0.50; desktop file exists warning in dialog box instead of in minibuffer

[Glenn Morris]

Eli Zaretskii wrote:

>> It seems that last-nonmenu-event (which y-or-no-p consults) is now nil
>> during startup, whereas it used to be 0.
>
> Perhaps because Qnil is now zero, and some variable defined 'static'
> and left uninitialized?

Anyway, nil seems like a reasonable default. I can't see that it was
intentionally 0 before.

Perhaps y-or-n-p and yes-or-no-p should also test that last-input-event
is non-nil before creating a dialog box?