[BUGFIX] Catch non existing directories for import syntax

Catch exceptions for non existing directories which are imported using
the @import syntax for TypoScript and return those as warning in the
template module.

Resolves: #86230
Releases: master
Change-Id: Ie4a6376407eeeaa7a717cb01ede5cabefa8a443f
Reviewed-on: https://review.typo3.org/58251


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>