[luatex] Segfault with null argument to -output-comment

[Hironori KITAGAWA]

Hello all,

LuaTeX raises a segmentation fault,
when -output-comment is just null:

--- a.tex ---
\expandafter\ifx\csname pdfoutput\endcsname\relax
   \else\pdfoutput0 \fi
abc\bye
---

$ luatex -output-comment= a.tex
This is LuaTeX, Version beta-0.80.0 (TeX Live 2015) (rev 5238)
  restricted \write18 enabled.
(./a.texzsh: segmentation fault (core dumped)  luatex -output-comment= a.tex

Other engines, such as tex, pdftex (and aleph) work fine:

$ tex -output-comment= a.tex
This is TeX, Version 3.14159265 (TeX Live 2015) (preloaded format=tex)
(./a.tex [1] )
Output written on a.dvi (1 page, 188 bytes).
Transcript written on a.log.

$ pdftex -output-comment= a.tex
This is pdfTeX, Version 3.14159265-2.6-1.40.16 (TeX Live 2015) 
(preloaded format=pdftex)
  restricted \write18 enabled.
entering extended mode
(./a.tex [1] )
Output written on a.dvi (1 page, 188 bytes).
Transcript written on a.log.

Regards
Hironori KITAGAWA <h_kitagawa2001 at yahoo.co.jp>