bug#28161: 26.0.50; Narrowing does not work reliably with flyspell

[Eli Zaretskii]

> From: Liu Hui <liuhui1610@gmail.com>
> Date: Sun, 20 Aug 2017 22:00:28 +0800
> 
> When I'm working with a narrowing buffer, `C-g' sometimes cancels the 
> narrowing accidentally. I find it only occurs when flyspell-mode is enabled.
> 
> Steps to reproduce:
> 
> 1. Emacs -Q
> 2. Create a buffer with several text lines, and turn on flyspell-mode
> 3. Select some text and press `C-x n n' to narrow the buffer
> 4. Type any letter and press `C-g' (sometimes twice) and `C-f' 
> (sometimes optional) quickly
> 
> => "Narrow" in mode-line disappears and all text are visible now

Thanks, fixed on the master branch.