[BUGFIX] Add fallback for language config

Currently, having a inlineLanguageLabelFiles
defined without passing any additional config
leads to an undefined key warning.

This has been fixed by adding a fallback
to an empty array.

Resolves: #103020
Releases: main
Change-Id: I4234a8efe5d33ee53afebbfe8d4fc36859b032ab
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/82762


Reviewed-by: Torben Hansen <derhansen@gmail.com>
Tested-by: Torben Hansen <derhansen@gmail.com>
Reviewed-by: Guido Schmechel <guido.schmechel@brandung.de>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: core-ci <typo3@b13.com>