NPE in `isExtractPayload()` method in `SimpleFunctionRegistry`.

[sobychacko]

This causes an NPE: https://github.com/spring-cloud/spring-cloud-function/blob/main/spring-cloud-function-context/src/main/java/org/springframework/cloud/function/context/catalog/SimpleFunctionRegistry.java#L1179

See this related issue in Spring Cloud Stream: spring-cloud/spring-cloud-stream#2934