[BUGFIX] Support \ArrayAccess objects with getter methods in ObjectAccess

In #66995 the extbase ObjectAccess has been cleaned up and introduced
a behavior where it is not possible anymore to call the getter of an
object that implements \ArrayAccess.
The problem is avoided by only using array-accessing if the offset
is found to exist. If not, the instance is handled as any other object.

Change-Id: Ie6b598d93fd7171d0b6c37259e424794861e31ed
Resolves: #78589
Related: #66995
Releases: master
Reviewed-on: https://review.typo3.org/50521


Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>