CompositeException when setting up notification

[EDLuke]

Describe the bug
It's very hard to reproduce this exception but we are seeing crashes caused by this in our production app. When notifications fail to be set up and at the same time a disconnection happens, RxJava seems to combine the two exceptions and throw a Fatal: CompositeException

To Reproduce
Steps to reproduce the behavior:

1. Throw exception at NotificationAndIndicationManager.java at line 241.
2. Disconnect the BLE peripheral

Expected behavior
Normal disconnect exception is handled and no Fatal: CompositeException that crashes the app.

Smartphone (please complete the following information):

• Device: Any
• OS: Any
• Library version: 2.1.1

Fatal Exception: io.reactivex.exceptions.CompositeException: 2 exceptions occurred. 
       at io.reactivex.internal.util.ExceptionHelper.addThrowable(ExceptionHelper.java:67)
       at io.reactivex.internal.util.AtomicThrowable.addThrowable(AtomicThrowable.java:34)
       at io.reactivex.internal.operators.observable.ObservableFlatMap$InnerObserver.onError(ObservableFlatMap.java:585)
       at io.reactivex.internal.operators.observable.ObservableFlatMap$MergeObserver.checkTerminate(ObservableFlatMap.java:511)
       at io.reactivex.internal.operators.observable.ObservableFlatMap$MergeObserver.drainLoop(ObservableFlatMap.java:334)
       at io.reactivex.internal.operators.observable.ObservableFlatMap$MergeObserver.drain(ObservableFlatMap.java:326)
       at io.reactivex.internal.operators.observable.ObservableFlatMap$InnerObserver.onError(ObservableFlatMap.java:590)
       at io.reactivex.internal.disposables.EmptyDisposable.error(EmptyDisposable.java:63)
       at io.reactivex.internal.operators.observable.ObservableError.subscribeActual(ObservableError.java:38)
       at io.reactivex.Observable.subscribe(Observable.java:12284)
       at io.reactivex.internal.operators.observable.ObservableFlatMap$MergeObserver.subscribeInner(ObservableFlatMap.java:165)
       at io.reactivex.internal.operators.observable.ObservableFlatMap$MergeObserver.onNext(ObservableFlatMap.java:139)
       at io.reactivex.internal.util.NotificationLite.accept(NotificationLite.java:246)
       at io.reactivex.internal.operators.observable.ObservableReplay$UnboundedReplayBuffer.replay(ObservableReplay.java:553)
       at io.reactivex.internal.operators.observable.ObservableReplay$ReplayObserver.replay(ObservableReplay.java:401)
       at io.reactivex.internal.operators.observable.ObservableReplay$ReplayObserver.onNext(ObservableReplay.java:366)
       at io.reactivex.internal.operators.observable.ObservableDoOnEach$DoOnEachObserver.onNext(ObservableDoOnEach.java:101)
       at io.reactivex.internal.operators.observable.ObservableElementAt$ElementAtObserver.onNext(ObservableElementAt.java:86)
       at com.jakewharton.rxrelay2.BehaviorRelay$BehaviorDisposable.test(BehaviorRelay.java:364)
       at com.jakewharton.rxrelay2.BehaviorRelay$BehaviorDisposable.emitNext(BehaviorRelay.java:358)
       at com.jakewharton.rxrelay2.BehaviorRelay.accept(BehaviorRelay.java:135)
       at com.polidea.rxandroidble2.internal.connection.DisconnectionRouter.onDisconnectedException(DisconnectionRouter.java:110)
       at com.polidea.rxandroidble2.internal.connection.RxBleGattCallback$2.onConnectionStateChange(RxBleGattCallback.java:81)
       at android.bluetooth.BluetoothGatt$1$4.run(BluetoothGatt.java:272)
       at android.bluetooth.BluetoothGatt.runOrQueueCallback(BluetoothGatt.java:780)
       at android.bluetooth.BluetoothGatt.access$200(BluetoothGatt.java:41)
       at android.bluetooth.BluetoothGatt$1.onClientConnectionState(BluetoothGatt.java:267)
       at android.bluetooth.IBluetoothGattCallback$Stub.onTransact(IBluetoothGattCallback.java:192)
       at android.os.Binder.execTransactInternal(Binder.java:1159)
       at android.os.Binder.execTransact(Binder.java:1123)

Caused by com.polidea.rxandroidble2.exceptions.BleCannotSetCharacteristicNotificationException: Cannot write client characteristic config descriptor (code 3) with characteristic UUID ********-****-****-****-************
       at com.polidea.rxandroidble2.internal.connection.NotificationAndIndicationManager$7.apply(NotificationAndIndicationManager.java:241)
       at com.polidea.rxandroidble2.internal.connection.NotificationAndIndicationManager$7.apply(NotificationAndIndicationManager.java:238)
       at io.reactivex.internal.operators.completable.CompletableResumeNext$ResumeNextObserver.onError(CompletableResumeNext.java:82)
       at io.reactivex.internal.operators.observable.ObservableIgnoreElementsCompletable$IgnoreObservable.onError(ObservableIgnoreElementsCompletable.java:61)
       at io.reactivex.internal.operators.observable.ObservableCreate$CreateEmitter.tryOnError(ObservableCreate.java:84)
       at com.polidea.rxandroidble2.internal.serialization.ConnectionOperationQueueImpl.flushQueue(ConnectionOperationQueueImpl.java:95)
       at com.polidea.rxandroidble2.internal.serialization.ConnectionOperationQueueImpl$1.run(ConnectionOperationQueueImpl.java:86)
       at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:462)
       at java.util.concurrent.FutureTask.run(FutureTask.java:266)
       at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
       at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
       at java.lang.Thread.run(Thread.java:923)

Caused by com.polidea.rxandroidble2.exceptions.BleDisconnectedException: Disconnected from MAC='C3:94:7B:7F:57:XX' with status 8 (GATT_INSUF_AUTHORIZATION or GATT_CONN_TIMEOUT)
       at com.polidea.rxandroidble2.internal.connection.RxBleGattCallback$2.onConnectionStateChange(RxBleGattCallback.java:81)
       at android.bluetooth.BluetoothGatt$1$4.run(BluetoothGatt.java:272)
       at android.bluetooth.BluetoothGatt.runOrQueueCallback(BluetoothGatt.java:780)
       at android.bluetooth.BluetoothGatt.access$200(BluetoothGatt.java:41)
       at android.bluetooth.BluetoothGatt$1.onClientConnectionState(BluetoothGatt.java:267)
       at android.bluetooth.IBluetoothGattCallback$Stub.onTransact(IBluetoothGattCallback.java:192)
       at android.os.Binder.execTransactInternal(Binder.java:1159)
       at android.os.Binder.execTransact(Binder.java:1123)

[dariuszseweryn]

A workaround for this is to set a RxJavaPlugins error handler and catch the CompositeException there.