InerfaceCast returns null for blueprint classes implementing that interface

Just for completion.
What was looking for is line 39.

//Wrong
IKinectListenerInterface = InterfaceCast<IKinectListenerInterface>(*It);

//Right
ListenerInterface  = InterfaceCast<IKinectListenerInterface>(*It);

Without that change the If check in Line 42 will not work because ListenerInterface is never changed and will be NULL.