Cannot sort a null object

[baoduoxu]

I encountered the following problems when building:

 Incremental build: disabled. Enable with --incremental
      Generating... 
      Remote Theme: Using theme zerostaticthemes/jekyll-serif-theme
       Jekyll Feed: Generating feed for posts
     Build Warning: Layout 'post' requested in _posts/2024-11-10-welcome-to-jekyll.markdown does not exist.
  Liquid Exception: Liquid error (line 18): Cannot sort a null object. in /tmp/jekyll-remote-theme-20241111-114331-3wj3d6/_layouts/teams.html
                    ------------------------------------------------
      Jekyll 4.3.4   Please append `--trace` to the `serve` command 
                     for any additional information or backtrace. 
                    ------------------------------------------------
/home/xubaoduo/uestc-auto/vendor/bundle/ruby/3.0.0/gems/jekyll-4.3.4/lib/jekyll/filters.rb:302:in `sort': Liquid error (line 18): Cannot sort a null object. (Liquid::ArgumentError)

The content of _config.yml is as follows, I changed the path item under defaults, but it does not work, services and teams can not be identified:

baseurl: '/'
permalink: pretty
title: 'Jekyll Serif'

logo:
  mobile: "images/logo/logo-mobile.svg"
  mobile_height: "32px"
  mobile_width: "32px"
  desktop: "images/logo/logo.svg"
  desktop_height: "32px"
  desktop_width: "120px"

home: 
  limit_services: 6

collections:
  services:
    output: true
    sort_by: weight
  team:
    output: true
    permalink: /team/:path/

defaults:
  - scope:
      path: "jekyll-serif-theme/_services"
      type: "services"
    values:
      layout: "service"
  - scope:
      path: "jekyll-serif-theme/_team"
      type: "team"
    values:
      layout: "team"

sass:
  style: compressed # possible values: nested expanded compact compressed

plugins:
  - jekyll-environment-variables

exclude:
  - Gemfile
  - Gemfile.lock
  - node_modules
  - vendor/bundle/
  - vendor/cache/
  - vendor/gems/
  - vendor/ruby/
  - LICENSE.md
  - LICENSE
  - README.md

Thanks!