[BUG] Runtime warnings in release 5.1.0

[stweil]

Description

While testing a (working) configuration with dfg-viewer 6.0 and presentation 5.1.0 I noticed several PHP warnings in the TYPO3 Administration Log:

Core: Error handler (BE): PHP Warning: Undefined array key "log_001" in /var/www/dfgviewer/public/typo3conf/ext/dlf/Classes/Common/Indexer.php line 334
Core: Error handler (FE): PHP Warning: Trying to access array offset on null in /var/www/dfgviewer/public/typo3conf/ext/dlf/Classes/Common/MetsDocument.php line 849
Core: Error handler (FE): PHP Warning: Undefined array key "creationDate" in /var/www/dfgviewer/public/typo3conf/ext/dlf/Classes/Common/MetsDocument.php line 849
Core: Error handler (FE): PHP Warning: Undefined array key "parentYear" in /var/www/dfgviewer/public/typo3conf/ext/dlf/Classes/Common/MetsDocument.php line 849
Core: Error handler (FE): PHP Warning: Undefined array key "parentAuthor" in /var/www/dfgviewer/public/typo3conf/ext/dlf/Classes/Common/MetsDocument.php line 849
[...]
Core: Error handler (FE): PHP Warning: Undefined array key "AUDIO" in /var/www/dfgviewer/public/typo3conf/ext/dlf/Classes/Controller/AudioPlayerController.php line 91
Core: Error handler (FE): PHP Warning: Undefined array key "page" in /var/www/dfgviewer/public/typo3conf/ext/dlf/Classes/Controller/AbstractController.php line 440
Core: Error handler (FE): PHP Warning: Undefined array key "page" in /var/www/dfgviewer/public/typo3conf/ext/dlf/Classes/Controller/AbstractController.php line 453
Core: Error handler (FE): PHP Warning: Undefined array key "multipleSource" in /var/www/dfgviewer/public/typo3conf/ext/dlf/Classes/Controller/AbstractController.php line 646
Core: Error handler (FE): PHP Warning: Undefined array key "docPage" in /var/www/dfgviewer/public/typo3conf/ext/dlf/Classes/Controller/PageViewController.php line 146
Core: Error handler (FE): PHP Warning: Undefined array key "multiview" in /var/www/dfgviewer/public/typo3conf/ext/dlf/Classes/Controller/PageViewController.php line 149
Core: Error handler (FE): PHP Warning: Undefined array key "multiview" in /var/www/dfgviewer/public/typo3conf/ext/dlf/Classes/Controller/PageViewController.php line 150
Core: Error handler (FE): PHP Warning: Undefined array key "measure" in /var/www/dfgviewer/public/typo3conf/ext/dlf/Classes/Controller/PageViewController.php line 530
Core: Error handler (FE): PHP Warning: Undefined array key "progressElementId" in /var/www/dfgviewer/public/typo3conf/ext/dlf/Classes/Controller/PageViewController.php line 537
Core: Error handler (FE): PHP Warning: Undefined array key "PHYS_0000" in /var/www/dfgviewer/public/typo3conf/ext/dlf/Classes/Controller/TableOfContentsController.php line 271
Core: Error handler (FE): PHP Warning: Undefined array key "DOWNLOAD" in /var/www/dfgviewer/public/typo3conf/ext/dlf/Classes/Controller/ToolboxController.php line 417
Core: Error handler (FE): PHP Warning: Trying to access array offset on null in /var/www/dfgviewer/public/typo3conf/ext/dlf/Classes/Controller/ToolboxController.php line 461
Core: Error handler (FE): PHP Warning: Undefined array key "files" in /var/www/dfgviewer/public/typo3conf/ext/dlf/Classes/Controller/ToolboxController.php line 461

Reproduction

Steps to reproduce the behaviour:

1. Install dfg-viewer 6.0 with a recent PHP version
2. Run viewer with some newspapers
3. Check TYPO3 protocol
4. See warnings

Expected Behavior

There should be no warnings. All (or at least) most of them were already fixed in the main branch. These fixes can be backported. Without such fixes, a heavily used productive instance will create huge log files.

Environment

• OS version: Debian GNU Linux trixie
• TYPO3 version: 11
• PHP version: 8.4 (or any other 8.* which is expected to produce the same warnings)

[stweil]

Here I collect more errors from the TYPO3 log file:

# This exception happens when an additional OAI-PMH page is loaded without a verb,
# but only if it is served from the TYPO3 cache (not directly after `vendor/bin/typo3 cache:flush`).
Exception: count(): Argument #1 ($value) must be of type Countable|array, string given, in file /var/customers/webs/weil/kitodo/public/typo3/sysext/frontend/Classes/ContentObject/ContentObjectRenderer.php:828