[BUGFIX] pageNotFound_handling never happens

The function \TYPO3\CMS\Core\Utility\RootlineUtility::getRecordArray
throws a \RuntimeException that should be caught in
\TYPO3\CMS\Frontend\Page\PageRepository::getRootline. If the exception
is not caught, the page-not-found-handling is never triggered.

Fixes: #44454
Releases: 6.0, 6.1
Change-Id: I3988b46ebaa8e479ed3c70017a5dda6bc5eaceac
Reviewed-on: https://review.typo3.org/18792
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn