I have just this post processor config (by accident):

```
"post.processors": "reselector", 
```

This should raise an error stating that "reselector" isn't configured, but instead I'm getting an NPE:

```
java.lang.NullPointerException: Cannot invoke "io.debezium.processors.spi.PostProcessor.configure(java.util.Map)" because "postProcessor" is null
    at io.debezium.processors.PostProcessorRegistryServiceProvider.lambda$createService$1(PostProcessorRegistryServiceProvider.java:36)
    at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:197)
    at java.base/java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1708)
    at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:509)
    at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:499)
    at java.base/java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:921)
    at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
    at java.base/java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:682)
    at io.debezium.processors.PostProcessorRegistryServiceProvider.createService(PostProcessorRegistryServiceProvider.java:38)
    at io.debezium.processors.PostProcessorRegistryServiceProvider.createService(PostProcessorRegistryServiceProvider.java:23)
    at io.debezium.service.DefaultServiceRegistry.createService(DefaultServiceRegistry.java:115)
    at io.debezium.service.DefaultServiceRegistry.createService(DefaultServiceRegistry.java:224)

```

This is with Debezium 3.1.0.