[bug] when buftype=quickfix, vim-whick-key will change the window where cursor stays

[Freed-Wu]

" $ 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/liuchengxu/vim-which-key
nnoremap <nowait> Z :<C-u>WhichKey 'Z'<CR>
setlocal buftype=quickfix
new
" $ vi -u test.vim

now cursor stays in the top window.

<C-W>j

now cusor stays in the bottom window.
Z

now cursor stays in a popup window.
<Esc>

now cursor don't return to the bottom window, it go to the top window.

it make some hotkey like ZZ close incorrect window.

I have test when the buftype is not quickfix (such as nofile, help) , the bug will not happen.

thanks.