cps-ncmp-service NullpointerException when DmiPluginRegistration has no additionProperties

When DMI requests a node to be registered in CPS it will send a request to CPS without additionalProperties (cmHandleProperties). 

In CPS we try to retrieve these but due to them being missing a NullPointerException is thrown and the registration fails @ NetworkCmProxyDataServiceImpl.updateDmiPluginRegistration() 

persistenceCmHandle.setAdditionalProperties(cmHandle.getCmHandleProperties());