This PR was merged into the 4.x branch.

Discussion
----------

Fix BC break for fields with deep objects

Since version 4.4 (#5343) having a field declared as:

```php
TextField::new('period.start');
```
will throw an exception if `period` is `null`.
This is because (as per documentation)

```php
   /**
     * ......
     * `@throws` Exception\InvalidArgumentException If the property path is invalid
     * `@throws` Exception\AccessException          If a property/index does not exist or is not public
     * `@throws` Exception\UnexpectedTypeException  If a value within the path is neither object
     *                                            nor array
     */
    public function getValue(object|array $objectOrArray, string|PropertyPathInterface $propertyPath): mixed;
```

`UnexpectedTypeException` is thrown if any object in the path is `null`.

This PR fixes this by catching the exception and simply marking it not readable to keep the BC

Commits
-------

b85867d Fix BC break for deep objects