bug#21419: isearch does not exit cleanly when ido active

[Noam Postavsky]

Ista Zahn <istazahn <at> gmail.com> wrote:
> Results: buffer contents remains font-locked with isearch face.
> Expected result: the final "C-g" should have exited from isearch
> mode, as happens when ido mode is not active.

I'm seeing the font-lock leftovers from isearch remaining without
ido-mode being active as well.

I think isearch-yank-kill is not intended as an entry point. Perhaps
it should have something like (unless isearch-mode (user-error
"isearch not active!"))
Or maybe
(unless isearch-mode (isearch-mode t))