"Warning: Undefined array key "REMOTE_USER" in [...]/lib/plugins/loadskin/action.php on line 130" when not logged in

[sychron]

environment:

• server runs php 8.3
• Fresh dokuwiki install, Release 2024-02-06b "Kaos"
• Settings: Everyone may read, only logged in users may modify
• Dokuwiki default template aktive
• authplain as auth method
• templates installed, but not active: Bootstrap3, Read The Dokus, WikiPraktik
• base plugins installed and active: ACL Manager, Plain Auth, Configuration Manager, Extension Manager, Info, logviewer, Revert
  Manager, safenrecode, styling, User Manager
• additional plugins installed and active: comment, folded, include, Pagelist, sorttablejs, Tag, Wrap

steps to reproduce:

• loadskin installed via extension manager

expected:

• wiki works as usual
• loadskin can be configured in admin panel

actual:

• error message shown on top of every page when not logged in:
  "Warning: Undefined array key "REMOTE_USER" in [...]/lib/plugins/loadskin/action.php on line 130"
  (shortened to not reveal server internals)

• error message in admin panel when logged in as admin:
  "Warning: Undefined variable $ID in [...]/lib/plugins/loadskin/admin.php on line 74"
  (shortened to not reveal server internals)

[sychron]

May be related to this: https://forum.dokuwiki.org/d/21686-tplmod-e-warning-undefined-array-key-remote-user