[BUGFIX] Fixes loading problem with RTEHtmlarea.

Related: forge.typo3.org/issues/65631

Classes/Xclass/LocalizationFactory.php

@@ -88,7 +88,7 @@ class LocalizationFactory extends \TYPO3\CMS\Core\Localization\LocalizationFacto
 					$this->localizationOverride($fileReference, $languageKey, $charset, $errorMode, $LOCAL_LANG);
 
 					// Save parsed data in cache
-					$this->store->setData($fileReference, $languageKey, $LOCAL_LANG[$languageKey]);
+					$this->store->setData($fileReference, $languageKey, (array) $LOCAL_LANG[$languageKey]);
 
 					// Cache processed data
 					$this->cacheInstance->set($hash, $this->store->getDataByLanguage($fileReference, $languageKey));