Required `message` field is missing from error response ContentModified

[kdarkhan]

I am using lua-language-server using nvim-lsp client.

When I try to jump to definition inside a file which has not completed loading, sometimes I get ContentModified error response.
https://github.com/sumneko/lua-language-server/blob/9744eb716f3b521f14331d4769925380c3dc3d84/script/proto/define.lua#L186

The response object has code but no message field.
Example here

{
  "code": -32801
}

That is causing the error in telescope-lsp handler which I am fixing in nvim-telescope/telescope.nvim#1630

I checked Language Server Protocol specification and it seems message field is required and cannot be omitted.
Link here

If I understand it correctly then lua-language-server should be returning an error response which always contains message field.

[kdarkhan]

Thanks.