bug#34272: 26.1.91 M-x flyspell-mode

[Tak Kunihiro]

I traced `ispell-find-hunspell-dictionaries' using Edebug.  I have an
impression, problem is something to do with initialization on
`hunspell-default-dict'.  The output is shown below.


* Recipe with success

CMD> c:\emacs-26.1\bin\runemacs.exe -Q
(setq ispell-program-name "c:/msys64/mingw64/bin/hunspell.exe")
M-x flyspell-mode

* Recipe with failure

CMD> c:\emacs-26.1.91\bin\runemacs.exe -Q
(setq ispell-program-name "c:/msys64/mingw64/bin/hunspell.exe")
M-x flyspell-mode

Error enabling Flyspell mode:
(stringp nil)

* Lines surveyed

ispell:1104: (defun ispell-find-hunspell-dictionaries ()
...
ispell:1187:    (setq hunspell-default-dict (or hunspell-multi-dict
ispell:1188:                                (car hunspell-default-dict)))
ispell:1189:    (setq hunspell-default-dict-entry
ispell:1190:      (ispell-parse-hunspell-affix-file hunspell-default-dict))

* Output by Edebug

ispell:1187: (setq hunspell-default-dict (or hunspell-multi-dict
ispell:1188:                                 (car hunspell-default-dict)))

hunspell-multi-dict                     ; => nil
hunspell-default-dict                   ; => nil
(car hunspell-default-dict)             ; => nil
(or hunspell-multi-dict
    (car hunspell-default-dict))        ; => nil
(setq hunspell-default-dict
      (or hunspell-multi-dict
          (car hunspell-default-dict))) ; => nil

ispell:1189: (setq hunspell-default-dict-entry
ispell:1189:       (ispell-parse-hunspell-affix-file hunspell-default-dict))

hunspell-default-dict                   ; => nil
(ispell-parse-hunspell-affix-file hunspell-default-dict) ; => crash