Actor components added natively can be set to null on derived blueprints during blueprint compilation

A native default subobject can be nulled out during compilation of the owning class in derived Blueprints with circular dependencies. 

Copied from linked UDN:

The setup:

• A native actor type, let's call it ANativeBaseActor.
• Blueprint actor derived from ANativeBaseActor, called BlueprintBaseActor.
• Another blueprint actor, this time derived from BlueprintBaseActor, I'll call this BlueprintDerivedActor.
• BlueprintBaseActor needs a circular dependency on BlueprintDerivedActor, I did this by casting "self" to a BlueprintDerivedActor in the event graph of BlueprintBaseActor.
• BlueprintDerivedActor needs to be a non-dataonly blueprint. I added a variable in blueprint and used it in the event graph.

The repro:

• Add a new component in the C++ class ANativeBaseActor and store it in a UPROPERTY

• • I used a scene component added it as a default subobject in the NativeBaseActor's constructor
• Load the editor and open BlueprintDerivedActor, observe the added component
• Open and compile BlueprintDerivedActor
• Note that the component is nulled out in the BlueprintDerivedActor