[BUGFIX] Correctly determine link type

Due to a wrong condition transformation the detection of external links
without schema is broken.
Revert the condition to the correct logic again as it was in 6.2.

Related: #55626
Resolves: #72818
Releases: master, 7.6
Change-Id: I1cd716c4a689db1309d28d750e30987eeee3efff
Reviewed-on: https://review.typo3.org/46082


Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>
Tested-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>
Reviewed-by: Stephan Großberndt <stephan@grossberndt.de>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>