Filter window not updated properly for split='no'

[KazMorita]

Problems summary

ddu-ui-ff does not renew the filter window properly when split='no'. When I enter the first letter for filtering, the filter window shows the result of filtering. The filter window no longer accepts input because it is showing filtered result, which is not modifiable. This is also reproduced in vim=v9.0.1676. It works perfectly fine when split='horizontal' is set.

Expected

The filter window should not show the filtered result. Even after the input of the first letter, it should retain the filtering window.

Environment Information

• ddu-ui-ff version (SHA1):a5238c6fea598f7b8f76d1c2ce280a7b01753aa5

• denops.vim version (SHA1):62b1d22b3e60fcc9e570a531a5af1e4b2393c15a

• deno version(deno -V output): deno 1.34.3

• OS: arch linux

• neovim/Vim :version output:

  
  NVIM v0.9.1
  Build type: Release
  LuaJIT 2.1.0-beta3
  
  system vimrc file: "$VIM/sysinit.vim"
  fall-back for $VIM: "/usr/share/nvim"

Run :checkhealth for more info

## Provide a minimal init.vim/vimrc without plugin managers (Required!)

```vim
set runtimepath^=~/.plugins/Shougo/ddu-commands.vim
set runtimepath^=~/.plugins/Shougo/ddu-filter-matcher_substring
set runtimepath^=~/.plugins/Shougo/ddu-source-file_old
set runtimepath^=~/.plugins/Shougo/ddu-ui-ff
set runtimepath^=~/.plugins/Shougo/ddu.vim
set runtimepath^=~/.plugins/vim-denops/denops.vim

call ddu#custom#patch_global({
\   'ui': 'ff',
\   'uiParams': {
\     'ff': {
\       'split': 'no',
\     },
\   },
\   'sourceOptions': {
\     '_': {
\       'matchers': ['matcher_substring'],
\     },
\   },
  \ })

nnoremap <SPACE>fo <Cmd>Ddu -name=find file_old<CR>

autocmd FileType ddu-ff call s:ddu_my_settings()
function! s:ddu_my_settings() abort
  nnoremap <buffer> i <Cmd>call ddu#ui#do_action('openFilterWindow')<CR>
endfunction

How to reproduce the problem from neovim/Vim startup (Required!)

1. press 'SPACE fo'
2. press 'i'
3. enter the first letter to filter and you will not be able to continue filtering.

[Shougo]

Fixed.