Only fontify emphasis markers when they are visible

* lisp/org.el (org-do-emphasis-faces): Only fontify emphasis
markers when they are visible.

Thanks to d.williams for provided a bug report and this fix.

lisp/org.el

@@ -5079,9 +5079,10 @@ stacked delimiters is N.  Escaping delimiters is not possible."
 		   ;; Do not span over cells in table rows.
 		   (not (and (save-match-data (org-match-line "[ \t]*|"))
 			     (string-match-p "|" (match-string 4))))))
-	    (pcase-let ((`(,_ ,face ,_) (assoc marker org-emphasis-alist)))
+	    (pcase-let ((`(,_ ,face ,_) (assoc marker org-emphasis-alist))
+			(m (if org-hide-emphasis-markers 4 2)))
 	      (font-lock-prepend-text-property
-	       (match-beginning 2) (match-end 2) 'face face)
+	       (match-beginning m) (match-end m) 'face face)
 	      (when verbatim?
 		(org-remove-flyspell-overlays-in
 		 (match-beginning 0) (match-end 0))