error executing autocmd for vim function `<SNR>58_vim_lsp_load_or_suggest`

im getting this error when opening files

Error while executing "BufRead autocmds for "*.vim"..FileType autocmds for "vim"..function <SNR>58_vim_lsp_load_or_suggest":
Line    8:
E712: Argument of extend() must be a list or directory

this is my configuration:

function! s:on_lsp_buffer_enabled() abort
    setlocal omnifunc=lsp#complete
    setlocal signcolumn=yes
    if exists('+tagfunc') | setlocal tagfunc=lsp#tagfunc | endif
    nmap <buffer> gd <plug>(lsp-definition)
    nmap <buffer> gs <plug>(lsp-document-symbol-search)
    nmap <buffer> gS <plug>(lsp-workspace-symbol-search)
    " nmap <buffer> gr <plug>(lsp-references)
    nmap <buffer> gi <plug>(lsp-implementation)
    nmap <buffer> gt <plug>(lsp-type-definition)
    nmap <buffer> <leader>rn <plug>(lsp-rename)
    nmap <buffer> [g <plug>(lsp-previous-diagnostic)
    nmap <buffer> ]g <plug>(lsp-next-diagnostic)
    nmap <buffer> K <plug>(lsp-hover)
    nnoremap <buffer> <expr><c-f> lsp#scroll(+4)
    nnoremap <buffer> <expr><c-d> lsp#scroll(-4)

    let g:lsp_format_sync_timeout = 1000
endfunction

augroup lsp_install
  au!
  " call s:on_lsp_buffer_enabled only for languages that has the
  " server registered.
  autocmd User lsp_buffer_enabled call s:on_lsp_buffer_enabled()
augroup END

let g:lsp_settings = {
    \  'clangd': {'cmd': ['clangd']},
    \  'efm-langserver': {'disabled': v:false}
    \}

and i installed vim-lsp using vim-plug: Plug 'prabirshrestha/vim-lsp'

prabirshrestha / vim-lsp

error executing autocmd for vim function `<SNR>58_vim_lsp_load_or_suggest` #1477