Improve guard so it works for no eof new line

ftplugin/latex-box/latexmk.vim

@@ -1,4 +1,5 @@
 if !exists('g:polyglot_disabled') || index(g:polyglot_disabled, 'latex') == -1
+
 " LaTeX Box latexmk functions
 
 " Options and variables {{{
@@ -553,4 +554,5 @@ endif
 " }}}
 
 " vim:fdm=marker:ff=unix:noet:ts=4:sw=4
+
 endif