[BUGFIX] Normalize category storage PID on TYPO3v12

The new TypoScript parser introduced in TYPO3v12 yields a regular integer in case of a single storagePid. Only in case of a CSV this will be a string. This in turn leads to explode() failing with a type error in the integer case.

Fix this by normalizing the setting value to string.

Fixes: #301

Classes/Domain/Repository/CategoryRepository.php

@@ -33,7 +33,7 @@ public function initializeObject(): void
             GeneralUtility::makeInstance(Context::class),
             $configurationManager
         );
-        $querySettings->setStoragePageIds(GeneralUtility::intExplode(',', $this->settings['persistence']['storagePid']));
+        $querySettings->setStoragePageIds(GeneralUtility::intExplode(',', (string)$this->settings['persistence']['storagePid']));
         $this->setDefaultQuerySettings($querySettings);
 
         $this->defaultOrderings = [