[BUGFIX] Fix usage of preparedStatement object in $query->statement

This is a follow-up fix for the integration of preparedStatements in
Extbase. Due to a wrong comparison, an own preparedStatement object
used in $query->statement() would never be executed.

Resolves: #57254
Releases: 6.2
Change-Id: I3176339be309530b50ff89410affa386d7f6f8e8
Reviewed-on: https://review.typo3.org/28726
Reviewed-by: Felix Oertel
Reviewed-by: Markus Klein
Tested-by: Markus Klein