In the MessageCorrelationBuilder it is not possible to set a property to null, for example the
business key. This is not consistent with other builders, for example with the ProcessInstantiationBuilderImpl. Also that means that a property can't be reset and the user have to check the value -> which makes no sense since the default value is null.
This ticket was migrated to github: https://github.com/camunda/camunda-bpm-platform/issues/2225. Please use this link for any future references and continue any discussion there.