[bug] conflict with startify

```vim
" $ uname -r
" 5.13.10-arch1-1
" $ has nvim
" ✓ nvim 0.5.0
" $ has python
" ✓ python 3.9.6
" $ cat test.vim
set runtimepath=$VIMRUNTIME
set runtimepath+=~/.local/share/nvim/repos/github.com/mhinz/vim-startify
set runtimepath+=~/.local/share/nvim/repos/github.com/junegunn/vim-peekaboo
" $ vi -u test.vim
```


Press `"`

Press ``

In the right of window, there exists a new window.

However, if `vi -u test.vim a`, the window will not exist.

Start by reproducing the conflict with the provided test.vim configuration, using vi -u test.vim and vi -u test.vim a. Compare the window behavior after pressing `"` and , then review the linked vim-startify issue for related investigation. Done means the extra window no longer appears in the first invocation while the relevant Peekaboo behavior remains intact.

Written by the indexing model from the issue text.