[BUGFIX] Ensure TranslateViewHelper does not fail on invalid extension

Change #95839 introduced a regression that causes TranslateViewHelper
to fail when an invalid extension key is specified. This patch restores
the previous behavior and avoids more regressions by a new test.

Resolves: #95957
Releases: master
Change-Id: I98675f94cf367b43f4123bb981f60c35286ace7a
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/72158


Tested-by: core-ci <typo3@b13.com>
Tested-by: Helmut Hummel <typo3@helhum.io>
Tested-by: Nikita Hovratov <nikita.h@live.de>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Helmut Hummel <typo3@helhum.io>
Reviewed-by: Nikita Hovratov <nikita.h@live.de>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>