Reformat changelog does not support unnamed section

[oddstr13]

Traceback (most recent call last):
  File "/home/runner/work/jellyfin-kodi/jellyfin-kodi/.github/tools/reformat_changelog.py", line 87, in <module>
    reformat(args.format, args.emoji)
  File "/home/runner/work/jellyfin-kodi/jellyfin-kodi/.github/tools/reformat_changelog.py", line 49, in reformat
    section["items"].append(gd)
KeyError: 'items'

https://github.com/jellyfin/jellyfin-kodi/actions/runs/6033384710/job/16369981650#step:5:56

https://github.com/jellyfin/jellyfin-kodi/blob/68c49ea4b7c3b57487dcb56f8564024bcb4e5926/.github/tools/reformat_changelog.py#L33-L49