bug#20448: 25.0.50; 25.0.50; `ispell-async-processp' set to nil causes an error from (ispell-start-process)

[Eli Zaretskii]

> From: Michael Pontus <m.pontus@gmail.com>
> Date: Tue, 28 Apr 2015 12:04:56 +0300
> 
> Steps to reproduce:
> 
> 1. Start emacs -Q
> 2. M-: (setq ispell-async-processp t)
> 3. M-: (ispell-start-process)

I'm astonished that someone wants to use the synchronous mode of
ispell.el, which was written and exists solely for the MSDOS build of
Emacs.

> Backtrace:
> 
>     Debugger entered--Lisp error: (wrong-type-argument stringp nil)
>       file-accessible-directory-p(nil)
>       ispell-start-process()
>       eval((ispell-start-process) nil)
>       eval-expression((ispell-start-process) 1)
>       funcall-interactively(eval-expression (ispell-start-process) 1)
>       call-interactively(eval-expression nil nil)
>       command-execute(eval-expression)
> 
> Following excerpt from ispell.el indicates that function
> `ispell-start-process' may return one of two types of values: process
> object or t, depending on the value of user-option in question.

ispell-async-processp is not a user option.

Anyway, I fixed this in commit e78aef0 on master.