check for actual helptag files

autoload/vundle/installer.vim

@@ -43,8 +43,9 @@ func! s:reload_bundles()
 endf
 
 func! s:has_doc(rtp)
-  return (isdirectory(a:rtp.'/doc')
-    \ && (!filereadable(a:rtp.'/doc/tags') || filewritable(a:rtp.'/doc/tags')))
+  return isdirectory(a:rtp.'/doc')
+    \ && (!filereadable(a:rtp.'/doc/tags') || filewritable(a:rtp.'/doc/tags'))
+    \ && (len(expand(a:rtp.'/doc/*.txt')) > 0 || len(expand(a:rtp.'/doc/*.??x')) > 0)
 endf
 
 func! s:helptags(rtp)