Checking receiver certificates may cause a NPE

[RovoMe]

On looking at the code that handles the sender certificate check I noticed that if a check for valid participantId, docTypeId or processId in _getReceiverEndpoint(...) fails null is returned that leads to execution of the respective null-check block, which performs operations on the previously tested objects, which may be null at this point,and therefore throw a NPE.

[phax]

You are totally right - thanks for pointing that out 👍

[phax]

Thanks again. Will be part of the 0.9.12 release