[BUGFIX] Do not render empty link explanation callout

In case a link does not set any additional
attributes, no empty callout is rendered.

Resolves: #102721
Releases: main, 12.4
Change-Id: I7ec4d7b64450112731363d721f4d49322448b41c
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/82294


Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Oliver Bartsch <bo@cedev.de>