[BUGFIX] Skip email reports in validator task if no email is set

Until TYPO3 CMS 10.4 the ValidatorTask could be used without
sending the validation report via email. The task could be used
to re-crawl all links and update the reports in the module only.

This behaviour is restored by sending emails only if an email address
is set.

Resolves: #97431
Releases: main, 12.4, 11.5
Change-Id: I63197605c272f56449f933abd08d0c05bd7a7661
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/79772


Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>