[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.

Resolves: #63701
Releases: master, 6.2
Change-Id: I047f45bd5199216aec6f37a0c9b0526c455cad92
Reviewed-on: http://review.typo3.org/35387
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>