[BUGFIX] EXT:indexed_search: Dont add stat record for empty search

Resolves: #81786
Releases: master, 8.7
Change-Id: I1bc5e93fdfb3a1068a09ae37c47e51b1811d58b5
Reviewed-on: https://review.typo3.org/53396


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Sascha Rademacher <s.rademacher@neusta.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Susanne Moog <susanne.moog@typo3.org>
Tested-by: Susanne Moog <susanne.moog@typo3.org>