Export: Fix bug when exporting to temporary buffer

When exporting to a temporary buffer, images to replace LaTeX
fragments cannot be produced, because there is no useful location
where they can be put.  Therefore, these images are not produced in
this case.

lisp/ChangeLog

@@ -1,3 +1,8 @@
+2009-03-20  Carsten Dominik  <carsten.dominik@gmail.com>
+
+	* org-exp.el (org-export-html-preprocess): Only create LaTeX
+	fragement images if there is an export file.
+
 2009-03-19  Carsten Dominik  <carsten.dominik@gmail.com>
 
 	* org-agenda.el (org-stuck-projects): Document that the subtree of

lisp/org-exp.el

@@ -3237,7 +3237,8 @@ Does include HTML export options as well as TODO and CATEGORY stuff."
 
 (defun org-export-html-preprocess (parameters)
   ;; Convert LaTeX fragments to images
-  (when (plist-get parameters :LaTeX-fragments)
+  (when (and org-current-export-file
+	     (plist-get parameters :LaTeX-fragments))
     (org-format-latex
      (concat "ltxpng/" (file-name-sans-extension
 			(file-name-nondirectory