If serialPersistentFields is defined with a value of null, serialization
behaves as if serialPersistentFields was not defined at all. This particular
case is not clearly addressed in the spec, but it seems intuitive that setting
serialPersistentFields to null should have the same effect as setting it to
an empty array of ObjectStreamFields (e.g., ObjectStreamClass.NO_FIELDS).

Code demonstrating the bug is attached.