[BUGFIX] FormFieldVH->getPropertyValue() must work without form object

Since the new property mapper is active by default it is
possible to create forms without object="{object}", e.g.
using a newAction. This leads to some view helpers throwing
an exception as they rely on a present object to receive the
property value. As this object may not be present a missing
check has to be added to method getPropertyValue().

This check also exists in Flow.Fluid and is necessary to
fix malfunctioning view helpers.

Releases: 6.2, 6.1
Resolves: #48750
Relates: #48628
Change-Id: I6c42725d6daf9003358f8b6fbe9af3e62f011213
Reviewed-on: https://review.typo3.org/21181
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
Reviewed-by: Alexander Schnitzler
Tested-by: Alexander Schnitzler
Reviewed-on: https://review.typo3.org/21220
[BUGFIX] Enable CheckboxViewHelper binding to ArrayObject and Null

Currently the checkbox view helper relies on a present
form object which is not necessary any longer since 6.1
as the new property mapper is active by default.

Therefore the viewhelper must be adjusted to be able to
be bound to ArrayObject objects or Null which throws an
exception till now.

Releases: 6.2, 6.1
Resolves: #48628
Change-Id: I35b70fb0a09ddd72da1c64ec5c7c5456e9af9471
Reviewed-on: https://review.typo3.org/21222
Reviewed-by: Anja Leichsenring
Tested-by: Anja Leichsenring