Getting Unknown function: neocomplete#smart_close_popup on backspace in insert mode
Hey,

I'm getting the following error:

`Unknown function: neocomplete#smart_close_popup`

When I hit backspace in insert mode.

Using the following init.toml:

```
# All SpaceVim option below [option] section
[options]
    filemanager = "nerdtree"
    sidebar_direction = 'left'
    # set spacevim theme. by default colorscheme layer is not loaded,
    # if you want to use more colorscheme, please load the colorscheme
    # layer
    colorscheme = "gruvbox"
    colorscheme_bg = "dark"
    # Disable guicolors in basic mode, many terminal do not support 24bit
    # true colors
    enable_guicolors = false
    # Disable statusline separator, if you want to use other value, please
    # install nerd fonts
    statusline_separator = "nil"
    statusline_iseparator = "bar"
    buffer_index_type = 4
    windows_index_type = 3
    enable_tabline_filetype_icon = false
    enable_statusline_mode = false
    statusline_unicode_symbols = false
    # Enable vim compatible mode, avoid changing origin vim key bindings
    vimcompatible = true

[[layers]]
name = "core"
filetree_show_hidden = true

[[layers]]
name = "git"

[[layers]]
name = "shell"

# Enable autocomplete layer
[[layers]]
name = 'autocomplete'
auto_completion_return_key_behavior = "complete"
auto_completion_tab_key_behavior = "cycle"

[[layers]]
name = 'shell'
default_position = 'top'
default_height = 30

[[layers]]
name = "lang#python"

[[layers]]
name = "lang#ruby"

[[layers]]
name = "lang#elixir"

[[layers]]
name = "lang#php"

[[layers]]
name = "lang#markdown"

[[layers]]
name = "fzf"
```

My vimrc:
```
if 1
    let g:_spacevim_if_lua = 0
    if has('lua')
        if has('win16') || has('win32') || has('win64')
            let s:plugin_dir = fnamemodify(expand('<sfile>'), ':h').'\lua'
            let s:str = s:plugin_dir . '\?.lua;' . s:plugin_dir . '\?\init.lua;'
        else
            let s:plugin_dir = fnamemodify(expand('<sfile>'), ':h').'/lua'
            let s:str = s:plugin_dir . '/?.lua;' . s:plugin_dir . '/?/init.lua;'
        endif
        silent! lua package.path=vim.eval("s:str") .. package.path
        if empty(v:errmsg)
            let g:_spacevim_if_lua = 1
        endif
    endif
    execute 'source' fnamemodify(expand('<sfile>'), ':h').'/config/main.vim'
endif

set mouse=a
let g:NERDTreeMouseMode=3
let g:NERDTreeWinPos = "left"

```

Note that I use ubuntu 20.04.2.

Any idea what could be the issue? Or what I should do for debugging?

Thanks