[BUGFIX] Prevent leading space for empty ATagParams

Currently a leading space will be returned by the ATagParams handler when
the $addGlobal parameter is TRUE.

This patch trims any space if no ATagParams have been configured.

Resolves: #52171
Releases: 6.2
Change-Id: I53b3723e530beb96ff0dc9606963c6d9928d4478
Reviewed-on: https://review.typo3.org/23954
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
Reviewed-by: Stefan Neufeind
Tested-by: Stefan Neufeind