Fix customization type of new variable

lisp/ChangeLog

@@ -3,6 +3,7 @@
 	* org-latex.el (org-latex-to-pdf-process): Fix typo in group tag.
 	(org-export-pdf-logfiles): New option.
 	(org-export-as-pdf): Use `org-export-pdf-logfiles'.
+	(org-export-pdf-logfiles): Fix customization type.
 
 	* org.el (org-insert-link): Improve error message when there is no
 	default link to select with RET.

lisp/org-latex.el

@@ -404,7 +404,7 @@ This function should accept the file name as its single argument."
   '("aux" "idx" "log" "out" "toc" "nav" "snm" "vrb")
   "The list of file extensions to consider as LaTeX logfiles."
   :group 'org-export-pdf
-  :type 'sexp)
+  :type '(repeat (string :tag "Extension")))
 
 (defcustom org-export-pdf-remove-logfiles t
   "Non-nil means, remove the logfiles produced by PDF production.