[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>

typo3/sysext/frontend/Classes/Http/RequestHandler.php

@@ -697,7 +697,7 @@ protected function processHtmlBasedRenderingSettings(TypoScriptFrontendControlle
                 if (is_array($languageFile)) {
                     continue;
                 }
-                $languageFileConfig = $typoScriptPageArray['inlineLanguageLabelFiles.'][$key . '.'];
+                $languageFileConfig = $typoScriptPageArray['inlineLanguageLabelFiles.'][$key . '.'] ?? [];
                 if (isset($languageFileConfig['if.']) && !$controller->cObj->checkIf($languageFileConfig['if.'])) {
                     continue;
                 }