bug#34535: 27.0.50; emacs -nw: while-no-input + sit-for + <KEY> => Quit

[Eli Zaretskii]

> Date: Fri, 22 Feb 2019 18:08:58 +0200
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 34535@debbugs.gnu.org
> 
> What happens on master is this: when sit-for is called inside
> while-no-input on a TTY, it returns the cons cell (t . ?\C-g), which
> then causes keyboard quit right after while-no-input returns.

I forgot to tell that sit-fore returns that cons cell because
read-event returns ?\C-g, regardless of what you type, when it is
called inside while-no-input.