NullPointerException: Cannot invoke "Object.getClass()" because "c" is null

[ribizli]

Describe the bug
When stopping a running application using FactusImpl.close() has a NPE.

Here the log entry:

WARN  [         DisposableBeanAdapter] Invocation of close method failed on bean with name 'factus': java.lang.NullPointerException: Cannot invoke "Object.getClass()" because "c" is null

After 30s the instance "dies" with the following exception on a subscribed projection:

WARN  [avouriteNetworkPointProjection] Unhandled onError:
org.factcast.core.store.RetryableException: io.grpc.StatusRuntimeException: UNAVAILABLE: Channel shutdownNow invoked
	at org.factcast.client.grpc.ClientExceptionHelper.from(ClientExceptionHelper.java:62)
	at org.factcast.client.grpc.ClientStreamObserver.onError(ClientStreamObserver.java:158)
	at io.grpc.stub.ClientCalls$StreamObserverToCallListenerAdapter.onClose(ClientCalls.java:481)
	at io.grpc.PartialForwardingClientCallListener.onClose(PartialForwardingClientCallListener.java:39)
	at io.grpc.ForwardingClientCallListener.onClose(ForwardingClientCallListener.java:23)
	at io.grpc.ForwardingClientCallListener$SimpleForwardingClientCallListener.onClose(ForwardingClientCallListener.java:40)
	at io.micrometer.core.instrument.binder.grpc.MetricCollectingClientCallListener.onClose(MetricCollectingClientCallListener.java:57)
	at io.grpc.internal.ClientCallImpl.closeObserver(ClientCallImpl.java:567)
	at io.grpc.internal.ClientCallImpl.access$300(ClientCallImpl.java:71)
	at io.grpc.internal.ClientCallImpl$ClientStreamListenerImpl$1StreamClosed.runInternal(ClientCallImpl.java:735)
	at io.grpc.internal.ClientCallImpl$ClientStreamListenerImpl$1StreamClosed.runInContext(ClientCallImpl.java:716)
	at io.grpc.internal.ContextRunnable.run(ContextRunnable.java:37)
	at io.grpc.internal.SerializingExecutor.run(SerializingExecutor.java:133)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
	at java.base/java.lang.Thread.run(Thread.java:833)
Caused by: io.grpc.StatusRuntimeException: UNAVAILABLE: Channel shutdownNow invoked
	at io.grpc.Status.asRuntimeException(Status.java:537)
	... 14 common frames omitted

FactCast Server/Client Version
0.7.4

To Reproduce
It just happens unpredictable, not every time.

Expected behavior
Shutdown without problems.

Additional context
For subscriptions the prisma-lib common-config-factus-subscribed-projections with version 2.3.1 is used.

The real cause cannot be retrieved, because the log fails with the NPE (I suppose):