Alpha fallback on last buffer close

init.lua

local install_path = vim.fn.stdpath 'data' .. '/site/pack/packer/start/packer.nvim'
local is_bootstrap = false
if vim.fn.empty(vim.fn.glob(install_path)) > 0 then
  is_bootstrap = true
  vim.fn.execute('!git clone https://github.com/wbthomason/packer.nvim ' .. install_path)
  vim.cmd [[packadd packer.nvim]]
end

require('packer').startup(function(use)
  use 'wbthomason/packer.nvim'
  use 'https://github.com/famiu/bufdelete.nvim'
  use {
    'goolord/alpha-nvim',
    requires = { 'kyazdani42/nvim-web-devicons' },
    config = function ()
        require'alpha'.setup(require'alpha.themes.startify'.config)
    end
  }

  if is_bootstrap then
    require('packer').sync()
  end
end)

vim.api.nvim_create_augroup("alpha_on_empty", { clear = true })
vim.api.nvim_create_autocmd("User", {
  pattern = "BDeletePost*",
  group = "alpha_on_empty",
  callback = function(event)
    local fallback_name = vim.api.nvim_buf_get_name(event.buf)
    local fallback_ft = vim.api.nvim_buf_get_option(event.buf, "filetype")
    local fallback_on_empty = fallback_name == "" and fallback_ft == ""

    if fallback_on_empty then
      vim.cmd("Alpha")
    end
  end,
})