[BUGFIX] Fix empty href parameter

In case the link target is not available (maybe hidden), the behaviour
known from the Core is to render the link text, but no a tag. The pageVH
renders the link, but the href parameter will be empty.

Resolves: #50751
Releases: 6.2, 6.1, 6.0
Change-Id: I526aa0e3d42f8aba867b3f996bac2366dc1f6d19
Reviewed-on: https://review.typo3.org/22789
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters