Improve guard so it works for no eof new line

indent/nix.vim

@@ -1,4 +1,5 @@
 if !exists('g:polyglot_disabled') || index(g:polyglot_disabled, 'nix') == -1
+
 " Vim indent file
 " Language:    Nix
 " Maintainer:  Daiderd Jordan <daiderd@gmail.com>
@@ -102,4 +103,5 @@ endfunction
 
 let &cpo = s:cpo_save
 unlet s:cpo_save
+
 endif