Some Mail instance can have a null name

java.lang.NullPointerException: null
        at com.google.common.base.Preconditions.checkNotNull(Preconditions.java:877)
        at org.apache.james.queue.rabbitmq.view.api.DeleteCondition.withName(DeleteCondition.java:170)
        at org.apache.james.queue.rabbitmq.Dequeuer.lambda$ack$1(Dequeuer.java:106)
        at com.github.fge.lambdas.consumers.ThrowingConsumer.accept(ThrowingConsumer.java:22)
        at org.apache.james.queue.rabbitmq.Dequeuer$RabbitMQMailQueueItem.done(Dequeuer.java:62)
        at org.apache.james.jmap.send.PostDequeueDecorator.done(PostDequeueDecorator.java:80)
        at org.apache.james.mailetcontainer.impl.JamesMailSpooler.lambda$run$0(JamesMailSpooler.java:164)