[PATCH] Fix XEmacs "wrong type error" in org-export-as-pdf

[Hugh Daschbach <hdasch@gmail.com>]

XEmacs throws a wrong-type-argument exception from org-export-as-pdf
if org file contains '&'.  See sample document, traceback, and patch
below.

This may well not be the best fix.  And it's not clear why this issue
doesn't exist in Emacs.  But there are several regular expressions in
org-export-latex-special-chars that call
org-export-latex-treat-backslash-char with a nil value for
string-after.  The regular expression that matched "MB&A" is
"\\(.\\|^\\)\\(&\\)".  So there is no (match-string 3).

Here's a document that generates the exception:

--8<---------------cut here---------------start------------->8---
* Header

MB&A

* Footer
--8<---------------cut here---------------end--------------->8---

Here's the traceback:

Debugger entered--Lisp error: (wrong-type-argument stringp nil)
  string-match("^[ \n	]" nil)
  (not (string-match "^[ \n	]" string-after))
  (and (not (string-match "^[ \n	]" string-after)) (not (string-match "[ 	]\\'\\|^" string-before)))
  (cond ((member ... org-html-entities) (concat string-before "$\\" ... "$")) ((and ... ...) (org-export-latex-protect-string ...)) ((not ...) (org-export-latex-protect-string ...)) ((and ... ...) (org-export-latex-protect-string ...)) (t (org-export-latex-protect-string ...)))
  org-export-latex-treat-backslash-char("B" nil)
  #<compiled-function (c) "...(304)" [sub-superscript match-data match-data match-data match-data c re-search-forward nil t get-text-property 2 org-protected match-string ("\\$" "$") "\\$" replace-match 1 "$" 3 ("&" "%" "#") "\\" "..." org-export-latex-protect-string "\\ldots{}" "~" 0 face org-link "\\~" "\\~{}" ("{" "}") match-data (...) org-inside-LaTeX-fragment-p (...) (...) org-export-latex-treat-backslash-char "" ("_" "^") (...) org-export-latex-treat-sub-super-char] 7>("\\(.\\|^\\)\\(&\\)")
  mapc-internal(#<compiled-function (c) "...(304)" [sub-superscript match-data match-data match-data match-data c re-search-forward nil t get-text-property 2 org-protected match-string ("\\$" "$") "\\$" replace-match 1 "$" 3 ("&" "%" "#") "\\" "..." org-export-latex-protect-string "\\ldots{}" "~" 0 face org-link "\\~" "\\~{}" ("{" "}") match-data (...) org-inside-LaTeX-fragment-p (...) (...) org-export-latex-treat-backslash-char "" ("_" "^") (...) org-export-latex-treat-sub-super-char] 7> ("^\\([^\n$]*?\\|^\\)\\(\\\\?\\$\\)\\([^\n$]*\\)$" "\\([a-za-z0-9]+\\|[ 	\n]\\|\\b\\|\\\\\\)\\(_\\|\\^\\)\\([a-za-z0-9]+\\|[ 	\n]\\|[:punct:]\\|{[a-za-z0-9]+}\\|([a-za-z0-9]+)\\)" "\\(.\\|^\\)\\(\\\\\\)\\([ 	\n]\\|[a-zA-Z&#%{}\"]+\\)" "\\(.\\|^\\)\\(&\\)" "\\(.\\|^\\)\\(#\\)" "\\(.\\|^\\)\\(%\\)" "\\(.\\|
 ^\\)\\({\\)" "\\(.\\|^\\)\\(}\\)" "\\(.\\|^\\)\\(~\\)" "\\(.\\|^\\)\\(\\.\\.\\.\\)"))
  mapc(#<compiled-function (c) "...(304)" [sub-superscript match-data match-data match-data match-data c re-search-forward nil t get-text-property 2 org-protected match-string ("\\$" "$") "\\$" replace-match 1 "$" 3 ("&" "%" "#") "\\" "..." org-export-latex-protect-string "\\ldots{}" "~" 0 face org-link "\\~" "\\~{}" ("{" "}") match-data (...) org-inside-LaTeX-fragment-p (...) (...) org-export-latex-treat-backslash-char "" ("_" "^") (...) org-export-latex-treat-sub-super-char] 7> ("^\\([^\n$]*?\\|^\\)\\(\\\\?\\$\\)\\([^\n$]*\\)$" "\\([a-za-z0-9]+\\|[ 	\n]\\|\\b\\|\\\\\\)\\(_\\|\\^\\)\\([a-za-z0-9]+\\|[ 	\n]\\|[:punct:]\\|{[a-za-z0-9]+}\\|([a-za-z0-9]+)\\)" "\\(.\\|^\\)\\(\\\\\\)\\([ 	\n]\\|[a-zA-Z&#%{}\"]+\\)" "\\(.\\|^\\)\\(&\\)" "\\(.\\|^\\)\\(#\\)" "\\(.\\|^\\)\\(%\\)" "\\(.\\|^\\)\\({\
 \)" "\\(.\\|^\\)\\(}\\)" "\\(.\\|^\\)\\(~\\)" "\\(.\\|^\\)\\(\\.\\.\\.\\)"))
  org-export-latex-special-chars(t)
  org-export-latex-content("\nMB&A\n\n")
  org-export-latex-first-lines(nil)
  org-export-as-latex(nil nil nil nil nil nil)
  org-export-as-pdf(nil)
  call-interactively(org-export-as-pdf)
  command-execute(org-export-as-pdf t)
  execute-extended-command(nil)
  call-interactively(execute-extended-command)
---
 lisp/org-export-latex.el |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/lisp/org-export-latex.el b/lisp/org-export-latex.el
index fa6a0e4..60795fb 100644
--- a/lisp/org-export-latex.el
+++ b/lisp/org-export-latex.el
@@ -976,6 +976,7 @@ The conversion is made depending of STRING-BEFORE and STRING-AFTER."
 	 (concat string-before "$\\"
 		 (or (cdar (member (list string-after) org-html-entities))
 		     string-after) "$"))
+	((null string-after) (concat string-before "\\"))
 	((and (not (string-match "^[ \n\t]" string-after))
 	      (not (string-match "[ \t]\\'\\|^" string-before)))
 	 ;; backslash is inside a word
-- 
1.5.6.3