[BUGFIX] PreparedStatement: count() must be an array or countable

Sanitize a count() call in PreparedStatement (8.7, 7.6 only)
for PHP 7.2 compatibility.

Change-Id: I8d3cac3814093c7223c6be8f8ab8dc8c610d28e1
Resolves: #83196
Releases: 8.7, 7.6
Reviewed-on: https://review.typo3.org/54912


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>