Improve guard so it works for no eof new line

ftplugin/swift.vim

@@ -1,6 +1,8 @@
 if !exists('g:polyglot_disabled') || index(g:polyglot_disabled, 'swift') == -1
+
 setlocal commentstring=//\ %s
 " @-@ adds the literal @ to iskeyword for @IBAction and similar
 setlocal iskeyword+=@-@,#
 setlocal completefunc=syntaxcomplete#Complete
+
 endif