[TASK] Remove converting pageNotFound_handling in bootstrap

On every request the pageNotFound_handling is casted to a real
boolean if needed. This is not needed and we fix the code execution
to catch this case. We gain not much with this change but makes the
bootstrap smaller.

Resolves: #54555
Releases: master
Change-Id: I2289eb6812f1626af513d9ac1bdfe96d41360212
Reviewed-on: https://review.typo3.org/49232


Tested-by: Bamboo TYPO3com <info@typo3.com>
Reviewed-by: Mathias Schreiber <mathias.schreiber@wmdb.de>
Tested-by: Mathias Schreiber <mathias.schreiber@wmdb.de>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>