GH-2723: Fix NPE in DelegatingInvocableHandler

Resolves #2723

Previously, it was possible for `handlerReturnsMessage` to return `null`
when a `cachedHandlers` was present, causing an NPE when unboxing the
`Boolean` value.

Ensure that the `handlerReturnsMessage` map is populated before adding
the handler to `cachedHandlers`.

**cherry-pick to 2.9.x**
# Conflicts:
#	spring-kafka/src/main/java/org/springframework/kafka/listener/adapter/DelegatingInvocableHandler.java

Author: garyrussell

spring-kafka/src/main/java/org/springframework/kafka/listener/adapter/DelegatingInvocableHandler.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2021 the original author or authors.
+ * Copyright 2016-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -217,8 +217,8 @@ protected InvocableHandlerMethod getHandlerForPayload(Class<? extends Object> pa
 			if (handler == null) {
 				throw new KafkaException("No method found for " + payloadClass);
 			}
-			this.cachedHandlers.putIfAbsent(payloadClass, handler); //NOSONAR
 			setupReplyTo(handler);
+			this.cachedHandlers.putIfAbsent(payloadClass, handler); //NOSONAR
 		}
 		return handler;
 	}