Improve guard so it works for no eof new line

compiler/fish.vim

@@ -1,4 +1,5 @@
 if !exists('g:polyglot_disabled') || index(g:polyglot_disabled, 'fish') == -1
+
 if exists('current_compiler')
     finish
 endif
@@ -6,4 +7,5 @@ let current_compiler = 'fish'
 
 CompilerSet makeprg=fish\ --no-execute\ %
 execute 'CompilerSet errorformat='.escape(fish#errorformat(), ' ')
+
 endif