In the 0-10 code path, when resuming a session we replay all the unacked messages in the replay buffer, after setting the redelivery flag.
However when doing so we need to check if the delivery properties are present.
The current implementation doesn't do so simply bcos the JMS client always sets delivery properties when sending messages.
However this results in a test failure (testResumeNonemptyReplayBuffer in Connection.java) and this code can be used in the future for QMF etc.. and they could potentially send messages without delivery props. So better to handle the null cases to avoid any NPE's.