[BUG] NPE #46325

Describe the bug
I discivered in our logs a bug related to servicebus library.
SDK version: 7.17.12

Exception or Stack Trace
reactor.core.Exceptions$ErrorCallbackNotImplemented: java.lang.NullPointerException: Cannot invoke "java.util.concurrent.atomic.AtomicBoolean.getAndSet(boolean)" because "this.isDisposed" is null
Caused by: java.lang.NullPointerException: Cannot invoke "java.util.concurrent.atomic.AtomicBoolean.getAndSet(boolean)" because "this.isDisposed" is null
at com.azure.messaging.servicebus.implementation.ServiceBusReactorReceiver.closeAsync(ServiceBusReactorReceiver.java:199)
at com.azure.core.amqp.implementation.ReactorReceiver.lambda$new$12(ReactorReceiver.java:203)
at reactor.core.publisher.FluxFlatMap$FlatMapMain.onNext(FluxFlatMap.java:386)
at io.opentelemetry.javaagent.shaded.instrumentation.reactor.v3_1.TracingSubscriber.onNext(TracingSubscriber.java:68)
at io.opentelemetry.javaagent.shaded.instrumentation.reactor.v3_1.TracingSubscriber.onNext(TracingSubscriber.java:68)
at reactor.core.publisher.Operators$MonoSubscriber.complete(Operators.java:1839)
at reactor.core.publisher.MonoCacheTime$CoordinatorSubscriber.signalCached(MonoCacheTime.java:337)
at reactor.core.publisher.MonoCacheTime$CoordinatorSubscriber.onNext(MonoCacheTime.java:354)
at reactor.core.publisher.Operators$MonoInnerProducerBase.complete(Operators.java:2636)
at reactor.core.publisher.SinkOneMulticast.subscribe(SinkOneMulticast.java:99)
at reactor.core.publisher.MonoCacheTime.subscribeOrReturn(MonoCacheTime.java:143)
at reactor.core.publisher.Flux.subscribe(Flux.java:8628)
at reactor.core.publisher.Flux.subscribeWith(Flux.java:8815)
at reactor.core.publisher.Flux.subscribe(Flux.java:8608)
at reactor.core.publisher.Flux.subscribe(Flux.java:8532)
at reactor.core.publisher.Flux.subscribe(Flux.java:8450)
at com.azure.core.amqp.implementation.ReactorReceiver.(ReactorReceiver.java:204)
at com.azure.messaging.servicebus.implementation.ServiceBusReactorReceiver.(ServiceBusReactorReceiver.java:76)
at com.azure.messaging.servicebus.implementation.ServiceBusAmqpLinkProvider.createReceiveLink(ServiceBusAmqpLinkProvider.java:45)
at com.azure.core.amqp.implementation.ConsumerFactory.createConsumer(ConsumerFactory.java:64)
at com.azure.core.amqp.implementation.ReactorSession.getSubscription(ReactorSession.java:672)
at com.azure.core.amqp.implementation.ReactorSession.lambda$createConsumer$11(ReactorSession.java:448)
at java.base/java.util.concurrent.ConcurrentHashMap.compute(ConcurrentHashMap.java:1916)
at com.azure.core.amqp.implementation.ReactorSession.lambda$createConsumer$12(ReactorSession.java:434)
at com.azure.core.amqp.implementation.handler.DispatchHandler.onTimerTask(DispatchHandler.java:32)
at com.azure.core.amqp.implementation.ReactorDispatcher$WorkScheduler.run(ReactorDispatcher.java:219)
at org.apache.qpid.proton.reactor.impl.SelectableImpl.readable(SelectableImpl.java:118)
at org.apache.qpid.proton.reactor.impl.IOHandler.handleQuiesced(IOHandler.java:61)
at org.apache.qpid.proton.reactor.impl.IOHandler.onUnhandled(IOHandler.java:398)
at org.apache.qpid.proton.engine.BaseHandler.onReactorQuiesced(BaseHandler.java:87)
at org.apache.qpid.proton.engine.BaseHandler.handle(BaseHandler.java:206)
at org.apache.qpid.proton.engine.impl.EventImpl.dispatch(EventImpl.java:108)
at org.apache.qpid.proton.reactor.impl.ReactorImpl.dispatch(ReactorImpl.java:324)
at org.apache.qpid.proton.reactor.impl.ReactorImpl.process(ReactorImpl.java:292)
at com.azure.core.amqp.implementation.ReactorExecutor.run(ReactorExecutor.java:91)
at io.opentelemetry.javaagent.shaded.instrumentation.reactor.v3_1.ContextPropagationOperator$RunnableWrapper.run(ContextPropagationOperator.java:373)
at reactor.core.scheduler.SchedulerTask.call(SchedulerTask.java:68)
at reactor.core.scheduler.SchedulerTask.call(SchedulerTask.java:28)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
at java.base/java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:304)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
at java.base/java.lang.Thread.run(Thread.java:840)

To Reproduce
I can't reproduce it locally. I don't know why it happens.
Ialso see we have a lot of errors like this:

com.azure.core.amqp.exception.AmqpException: The operation did not complete within the allotted timeout of 00:00:09. The time allotted to this operation may have been a portion of a longer timeout. For more information on exception types and proper exception handling, please refer to https://aka.ms/ServiceBusExceptions . TrackingId:b9845c9e-ff60-406a-a019-3791539096df_B4, SystemTracker:gi::G0:852012554:session-_5e9a38_1754641630975, bi::link17259775(852012557_G0), Timestamp:2025-08-08T08:27:20 TrackingId:601dc5c7b2974d6391632461b29f7f8b_G0, SystemTracker:gateway10, Timestamp:2025-08-08T08:27:20, errorContext[NAMESPACE: sbus-nonprod-sprint-main-pextnk.servicebus.windows.net. ERROR CONTEXT: N/A, PATH: slot_delivery_events_subscription_queue, REFERENCE_ID: session-_5e9a38_1754641630975, LINK_CREDIT: 0]

Code Snippet
Code to create listener:
private ServiceBusProcessorClient createQueueConsumer(String queuePath, QueueListenerProperties queueListenerProperties) {

    ServiceBusClientBuilder.ServiceBusProcessorClientBuilder builder = new ServiceBusClientBuilder()
            .connectionString(serviceBusProperties.getConnectionString())
            .retryOptions(retryOptions(queueListenerProperties))
            .processor()
            .maxConcurrentCalls(20)
            .queueName(queuePath);
    builder.processMessage(messageHandler);
    builder.processError(errorHandler);
    return builder.buildProcessorClient();
}

private static AmqpRetryOptions retryOptions(QueueListenerProperties properties) {
    AmqpRetryOptions o = new AmqpRetryOptions();
    o.setTryTimeout(Duration.ofSeconds(10);
    o.setMode(AmqpRetryMode.FIXED);
    return o;
}

Expected behavior
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Screenshots
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Setup (please complete the following information):

• OS: Azure AKS
• IDE: [e.g. IntelliJ]
• Library/Libraries: [e.g. com.azure:azure-core:1.16.0 (groupId:artifactId:version)]
• Java version: 17
• App Server/Environment: Azure AKS
• Frameworks: Spring Boot 2.7

Additional context
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• Bug Description Added
• Repro Steps Added
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