[BUGFIX] Enforce int for timestamp on DateTime mapping

This patch ensures using an integer value for turning a timestamp
to a DateTime object as otherwise a PHP error is thrown.

Resolves: #84962
Releases: master, 8.7, 7.6
Change-Id: I18e82c8f91f42c29c4014985a1ad11671b5a31f4
Reviewed-on: https://review.typo3.org/56914
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>

typo3/sysext/extbase/Classes/Persistence/Generic/Mapper/DataMapper.php

@@ -334,7 +334,7 @@ protected function mapDateTime($value, $storageFormat = null, $targetType = 'Dat
             return $utcDateTime->setTimezone($currentTimeZone);
         }
         // integer timestamps are local server time
-        return \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance($targetType, date('c', $value));
+        return \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance($targetType, date('c', (int)$value));
     }
 
     /**