Unable to call method "getType" of non-object "object" on deserialization

[vertisan]

Q	A
Bug report?	yes
Feature request?	no
BC Break report?	no
RFC?	no

Steps required to reproduce the problem

1. Enable Expression Language exclusion strategy as per: https://jmsyst.com/libs/serializer/master/cookbook/exclusion_strategies#dynamic-exclusion-strategy
2. Use the object variable in a expression within the Expose annotation on a class property, like so:

@JMS\Exclude(if="object.getType() === constant('\\App\\Model\\Resource\\ResourceObject::DIRECTORY_TYPE')")

3. Call deserialize on a string using this class, like so:

$serializer->deserialize($requestBody, 'MyClass', 'json');

4. Receive exception:

Unable to call method "getType" of non-object "object".

Expected Result

• I expect a successful deserialization.

Actual Result

• Deserialization failed with above exception message.