[BUGFIX] Ensure argument is an array in ContentObjectRenderer

This patch ensures that at least an empty array is passed to the
array_replace_recursive function to avoid warnings during rendering.

Inspired by Markus Klein

Resolves: #62139
Releases: master, 6.2
Change-Id: I854b39d7ff54c213bda00dd9060c1e5ee89914eb
Reviewed-on: http://review.typo3.org/33263
Reviewed-by: Markus Klein <klein.t3@reelworx.at>
Tested-by: Markus Klein <klein.t3@reelworx.at>