[CLEANUP] Replace count with empty in EXT:core

Replace occurences of count() with matching empty() pendants.

Resolves: #67778
Releases: master
Change-Id: I16c0299db8afda4c0fe406f7465a41d5eee3dd88
Reviewed-on: http://review.typo3.org/40686


Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Frederic Gaus <frederic.gaus@flagbit.de>
Tested-by: Frederic Gaus <frederic.gaus@flagbit.de>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>