Skip BufRead for an unnamed empty buffer (#1341)

Loading a plugin on demand triggers BufRead to apply ftdetect and ftplugin files, but there is nothing to detect in an unnamed empty buffer such as the one Vim creates on startup.

Signed-off-by: Yasuhiro Matsumoto <mattn.jp@gmail.com>

plug.vim

@@ -570,6 +570,10 @@ function! s:doautocmd(...)
 endfunction
 
 function! s:dobufread(names)
+  " Nothing to detect in an unnamed empty buffer, e.g. the one on startup
+  if empty(bufname('%')) && line('$') == 1 && empty(getline(1))
+    return
+  endif
   for name in a:names
     let path = s:rtp(g:plugs[name])
     for dir in ['ftdetect', 'ftplugin', 'after/ftdetect', 'after/ftplugin']