ox: Tiny refactoring

* lisp/ox.el (org-export-resolve-fuzzy-link): Use `string-to-char'
  instead of (aref STRING 0).

lisp/ox.el

@@ -4032,7 +4032,7 @@ Return value can be an object, an element, or nil:
 Assume LINK type is \"fuzzy\".  White spaces are not
 significant."
   (let* ((raw-path (org-element-property :path link))
-	 (match-title-p (eq (aref raw-path 0) ?*))
+	 (match-title-p (eq (string-to-char raw-path) ?*))
 	 ;; Split PATH at white spaces so matches are space
 	 ;; insensitive.
 	 (path (org-split-string