Error on 1st time running `NvimTreeToggle` (lazy load on command)

[folliehiyuki]

OS
Alpine Linux (edge)

Neovim version

NVIM v0.6.1
Build type: MinSizeRel
LuaJIT 2.1.0-beta3
Compiled by buildozer@build-edge-x86_64

Features: +acl +iconv +tui
See ":help feature-compile"

   system vimrc file: "$VIM/sysinit.vim"
  fall-back for $VIM: "/usr/share/nvim"

Run :checkhealth for more info

Nvim-tree version
Latest commit from master branch

Describe the bug
nvim-tree errors out on 1st run with command NvimTreeToggle.
Using NvimTreeOpen works fine.
If update_cwd = false, nvim-tree will error out on closing the tree buffer the 1st time.

To Reproduce

1. Lazy load nvim-tree with this config:

use {
  'kyazdani42/nvim-tree.lua',
  requires = 'kyazdani42/nvim-web-devicons',
  cmd = {'NvimTreeToggle', 'NvimTreeOpen'},
  config = function()
    require('nvim-tree').setup {
      update_focused_file = {enable = true, update_cwd = true}
    }
  end
}

2. Start Neovim, and run command :NvimTreeToggle
3. nvim-tree gives error:

E5108: Error executing lua ...vim/site/pack/packer/opt/packer.nvim/lua/packer/load.lua:165: Vim(echomsg)
:E114: Missing quote: "Error in packer_compiled: ...vim/site/pack/packer/opt/packer.nvim/lua/packer/load
.lua:83: Vim(lua):E5108: Error executing lua ...vim/site/pack/packer/opt/nvim-tree.lua/lua/nvim-tree.lua
:147: attempt to index global 'TreeExplorer' (a nil value)
stack traceback:
        [C]: in function 'cmd'
        ...vim/site/pack/packer/opt/packer.nvim/lua/packer/load.lua:165: in function <...vim/site/pack/p
acker/opt/packer.nvim/lua/packer/load.lua:161>
        [string ":lua"]:1: in main chunk

Expected behavior
NvimTree opens the buffer without any errors.

Additional context
Since NvimTreeOpen runs fine while NvimTreeToggle doesn't, the error clearly happens on https://github.com/kyazdani42/nvim-tree.lua/blob/c226eaf0bf09afedb5e9e2bda3c0bd4e8281a516/lua/nvim-tree.lua#L29-L31
but I don't know why.

[kyazdani42]

I'm going to take on a few refactorings this weekend for the startup/view management, i hope i'll be able to fix this somehow.