[BUGFIX] Always send strings to the method createStream

PHP8.1 throws an TypeError if we sending null to createStream

Resolves: #98417
Releases: main, 11.5
Change-Id: I327751c2cb13991122c84f4333a4976b9d0a0dae
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/76197


Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>