LaTeX Export: Better error message for emphasis alist conflicts

lisp/ChangeLog

@@ -3,6 +3,8 @@
 	* org-export-latex.el (org-export-as-latex)
 	(org-export-latex-first-lines): Avoid modification flag when
 	adding or removing text properties.
+	(org-export-latex-fontify): Catch error when org-emph-alist has
+	entries that are not defined for LaTeX export.
 
 	* org.el (orgstruct++-mode): New function.
 	(turn-on-orgstruct++): Call `orgstruct++-mode'.

lisp/org-export-latex.el

@@ -1213,6 +1213,9 @@ The conversion is made depending of STRING-BEFORE and STRING-AFTER."
 	  (beg (match-beginning 0))
 	  (end (match-end 0))
 	  rpl)
+      (unless emph
+	(message "`org-export-latex-emphasis-alist' has no entry for formatting triggered by \"%s\""
+		 (match-string 3)))
       (unless (or (get-text-property (1- (point)) 'org-protected)
 		  (save-excursion
 		    (goto-char (match-beginning 1))