application failed to start if implementing AsyncConfiurer without overriding getAsyncExecutor

[winster]

See the sample application https://github.com/winster/spring-tracer

You can see that application failed to start. This is because, application has implemented AsyncConfigurer (com.example.springboottracer.scheduler.AsyncConfiguration.java) but overriding only getAsyncUncaughtExceptionHandler. This will make TracedExecutor::delegate null and ends up in NullpointedException. As getAsyncExecutor is Nullable according to Spring, I think it may be good to handle this scenario in library. Atleast in my original application, I don't want to define a custom executor.

ps: Thank you so much for your efforts. The library is providing amazing feature and the team is really grateful to have it.