[BUGFIX] Avoid exception in presets of Install Tool

The method str_contains requires the 1st argument to be a string.
So we need to ensure that it is a string.

(It can be `null` if the command ran into an error.)

Resolves: #101349
Related: #70869
Releases: main, 12.4, 11.5
Change-Id: Ic4267f1fd8290d340b5fc43acd47797b592d466e
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/80032


Tested-by: core-ci <typo3@b13.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Oliver Bartsch <bo@cedev.de>