Revert "[CLEANUP] Replace strlen() with === for zero length check"

This reverts commit de27a20afbd8f413f60029afc5622c7b33212322

Change-Id: I078d2f7bbff605c91d83a9853e8feb9c31d57ccc
Reviewed-on: https://review.typo3.org/27792
Reviewed-by: Stefan Neufeind
Tested-by: Stefan Neufeind