help.syntax: Don't throw a sequence error when article is defined poo…

…rly.

basis/help/syntax/syntax.factor

@@ -1,8 +1,7 @@
 ! Copyright (C) 2005, 2009 Slava Pestov.
 ! See http://factorcode.org/license.txt for BSD license.
-USING: accessors arrays compiler.units definitions effects
-effects.parser help help.topics kernel namespaces parser
-sequences vocabs vocabs.parser words ;
+USING: accessors arrays compiler.units definitions help
+help.topics kernel math parser sequences vocabs.parser words ;
 IN: help.syntax
 
 SYNTAX: HELP:
@@ -11,9 +10,13 @@ SYNTAX: HELP:
     [ [ \ ; parse-until >array ] dip set-word-help ]
     bi ;
 
+ERROR: article-expects-name-and-title got ;
+
 SYNTAX: ARTICLE:
     location [
-        \ ; parse-until >array [ first2 ] [ 2 tail ] bi <article>
+        \ ; parse-until >array
+        dup length 2 < [ article-expects-name-and-title ] when
+        [ first2 ] [ 2 tail ] bi <article>
         over add-article >link
     ] dip remember-definition ;