Improve guard so it works for no eof new line

syntax/dart.vim

@@ -1,4 +1,5 @@
 if !exists('g:polyglot_disabled') || index(g:polyglot_disabled, 'dart') == -1
+
 " Vim syntax file " Language: Dart
 " Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 " for details. All rights reserved. Use of this source code is governed by a
@@ -134,4 +135,5 @@ let b:spell_options = "contained"
 if g:main_syntax is# 'dart'
   unlet g:main_syntax
 endif
+
 endif