Error executing vim.schedule lua callback using R language server

[DoktorMike]

I got the following error message:

Error executing vim.schedule lua callback: ...ael/.vim/plugged/diagnostic-nvim/lua/diagnostic/util.lua:185: attempt to compare string with number

Plugins:

- SimpylFold: OK
- fzf: OK
- vimwiki: OK
- fzf.vim: OK
- vim-slime: OK
- nord-vim: OK
- vim-snippets: OK
- completion-nvim: OK
- vim-devicons: OK
- black: OK
- vim-toml: OK
- diagnostic-nvim: OK
- ultisnips: OK
- wmgraphviz.vim: OK
- vim-fugitive: OK
- nvim-lspconfig: OK
- csv.vim: OK
- previm: OK
- nerdtree: OK
- julia-vim: OK
- vim-airline: OK
- vimtex: OK
- stan.vim: OK

Updated to the latest versions today 2020-09-29. Neovim version

NVIM v0.5.0-709-g4f8d98e58
Build type: RelWithDebInfo
LuaJIT 2.1.0-beta3
Compilation: /usr/bin/gcc-5 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=1 -O2 -g -Og -g -Wall -Wextra -pedantic -Wno-unused-parameter -Wstrict-prototypes -std=gnu99 -Wshadow -Wconversion -Wmissing-prototypes -Wvla -fstack-protector-strong -fno-common -fdiagnostics-color=auto -DINCLUDE_GENERATED_DECLARATIONS -D_GNU_SOURCE -DNVIM_MSGPACK_HAS_FLOAT32 -DNVIM_UNIBI_HAS_VAR_FROM -DMIN_LOG_LEVEL=3 -I/home/travis/build/neovim/bot-ci/build/neovim/build/config -I/home/travis/build/neovim/bot-ci/build/neovim/src -I/home/travis/build/neovim/bot-ci/build/neovim/.deps/usr/include -I/usr/include -I/home/travis/build/neovim/bot-ci/build/neovim/build/src/nvim/auto -I/home/travis/build/neovim/bot-ci/build/neovim/build/include
Compiled by travis@travis-job-6c0c5b42-8f4c-41ab-9dd7-cb182e87f565

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

   system vimrc file: "$VIM/sysinit.vim"
  fall-back for $VIM: "
/home/travis/build/neovim/bot-ci/build/neovim/build/nvim.AppDir/usr/share/nvim