[BUGFIX] Avoid exceptions during indexing with indexed_search

The exception "you need to add at least one set of values before
generating the SQL" occurs if the bulkInsert is triggered with
empty values. A check must be done before trying the query.

Resolves: #81140
Releases: master, 8.7
Change-Id: Ia0fe09e49d8e4b8341bda64ee248284c7ca2f3bd
Reviewed-on: https://review.typo3.org/52704


Reviewed-by: Josef Glatz <josef.glatz@typo3.org>
Tested-by: Josef Glatz <josef.glatz@typo3.org>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>