Show completion item detail when there is no documentation (#1133)

Co-authored-by: mattn <[email protected]>

Author: tsufeki

autoload/lsp/internal/completion/documentation.vim

@@ -64,7 +64,7 @@ function! s:resolve_completion(event) abort
             \ }})
             \ )
     else
-        return lsp#callbag#of({})
+        return lsp#callbag#of(l:managed_user_data)
     endif
 endfunction