If you want to subscribe a component type to a message type you have to set m_CurrentComponent to the component type ID and pass the message type ID as parameter to SubscribeToMessageType. Note that m_CurrentComponent is privat and SubscribeToMessageType is public.
With this patch the component type ID and the massage type ID are passed to SubscribeToMessageType.
There is more to type but the dependency is cleaner.
The compiler propably likes this aproach more it could use constant propagation to eliminate the ENSURE.
Since the component type ID has to be passed every time it is more likly to be wrong.