Autoclose not working

[samyak-jain]

Describe the bug
I have enabled mkdp_auto_close. Yet when I do :MarkdownPreviewStop or when I close the buffer, the preview window doesn't close

To Reproduce
Steps to reproduce the behavior:

I have set mkdp_browserfunc to the following

  function OpenURL(url)
    execute 'silent' '!qutebrowser' '--target' 'private-window' shellescape(a:url)
  endfunction

Expected behavior
The preview window to close when closing the buffer.

Desktop (please complete the following information):

• OS: 5.11.7-arch1-1