[FOLLOWUP][BUGFIX] Clear affected caches on page publishing

Prevent accessing an array key of a non-array.

Resolves: #37952
Releases: master, 6.2
Change-Id: I42de4ae3fb2f697a1bdcde323cd33ba68018af28
Reviewed-on: http://review.typo3.org/42309


Reviewed-by: Sascha Wilking <sascha.wilking@hmmh.de>
Tested-by: Sascha Wilking <sascha.wilking@hmmh.de>
Reviewed-by: Susanne Moog <typo3@susannemoog.de>
Tested-by: Susanne Moog <typo3@susannemoog.de>