Improve guard so it works for no eof new line

compiler/nim.vim

@@ -1,4 +1,5 @@
 if !exists('g:polyglot_disabled') || index(g:polyglot_disabled, 'nim') == -1
+
 if exists("current_compiler")
   finish
 endif
@@ -24,4 +25,5 @@ unlet s:cpo_save
 
 let g:syntastic_nim_checkers = ['nim']
 
+
 endif