PropertyAccessor - valid propertypath for array access with null value to be returned throws exception

[msumme]

This is in version 2.5.

I have an array like the following:

$myArray = ['property1' => ['property2' => null]];

If I call it throws an exception instead of returning null

$propertyAccessor = new PropertyAccessor(false, true);
$propertyAccessor->getValue($myArray, '[property1][property2]');
// NoSuchIndexException with message 'Cannot read property "property2". Available properties are "Array(
//  [0] => property2
// )
// ""

This is because line 232:
https://github.com/symfony/symfony/blob/2.5/src/Symfony/Component/PropertyAccess/PropertyAccessor.php#L232

It uses "isset()" instead of "array_key_exists" - and therefore falsely believes there is no property in the array - as isset() returns true on null values.