The PageTitleProviderManager will now check if the page cache object
is an instance of FrontendInterface before getting the value from cache.

Resolves: #87116
Releases: master
Change-Id: I14838b41a7cba653d5f4e6c875c647f547673644
Reviewed-on: https://review.typo3.org/59082


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Susanne Moog <susanne.moog@typo3.org>
Tested-by: Susanne Moog <susanne.moog@typo3.org>
Reviewed-by: Oliver Hader <oliver.hader@typo3.org>
Tested-by: Oliver Hader <oliver.hader@typo3.org>