[BUGFIX] Linkvalidator: Removed call to deprecated method render()

Call of FlashMessage->render() if user not have access to these listings
and when no broken links to be displayed were replaced with appropriate
code.

Resolves: #73576
Releases: master, 7.6
Change-Id: I86ce5c1dd49ea40aeb26be8f9da1060b1f6dc65d
Reviewed-on: https://review.typo3.org/46792


Reviewed-by: Daniel Goerz <ervaude@gmail.com>
Tested-by: Daniel Goerz <ervaude@gmail.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>