[BUGFIX] mysqli_stmt::reset may throw a PHP warning

Releases: master, 6.2
Resolves: #63080
Change-Id: Ib8e8720855b28c4d3782cec68c65da99cfe973af
Reviewed-on: http://review.typo3.org/34358
Reviewed-by: Mathias Schreiber <mathias.schreiber@wmdb.de>
Reviewed-by: Xavier Perseguers <xavier@typo3.org>
Tested-by: Xavier Perseguers <xavier@typo3.org>
Reviewed-by: Markus Klein <klein.t3@reelworx.at>
Tested-by: Markus Klein <klein.t3@reelworx.at>