org-export: Minor fixes

* contrib/lisp/org-export.el (org-export-creator-string):
Check for `org-version' being bound before using it.
(org-export-get-inbuffer-options): Use
`org-element-restriction'.

contrib/lisp/org-export.el

@@ -308,7 +308,9 @@ If the value is `comment' insert it as a comment."
 	  (const :tag "Insert the sentence" t)))
 
 (defcustom org-export-creator-string
-  (format "Generated by Org mode %s in Emacs %s." org-version emacs-version)
+  (format "Generated by Org mode %s in Emacs %s."
+	  (if (boundp 'org-version) org-version "(Unknown)")
+	  emacs-version)
   "String to insert at the end of the generated document."
   :group 'org-export-general
   :type '(string :tag "Creator string"))
@@ -1055,10 +1057,7 @@ Assume buffer is in Org mode.  Narrowing, if any, is ignored."
 			    (t
 			     (list
 			      key
-			      (let ((restr
-				     (cdr
-				      (assq 'macro
-					    org-element-object-restrictions))))
+			      (let ((restr (org-element-restriction 'macro)))
 				(org-element-parse-secondary-string
 				 ;; If user explicitly asks for
 				 ;; a newline, be sure to preserve it
@@ -1126,8 +1125,7 @@ Assume buffer is in Org mode.  Narrowing, if any, is ignored."
 		    (plist-put
 		     plist prop
 		     (org-element-parse-secondary-string
-		      value
-		      (cdr (assq 'keyword org-element-string-restrictions))))))))
+		      value (org-element-restriction 'keyword)))))))
 	org-element-parsed-keywords))
      ;; 3. Return final value.
      plist)))