Spring Change Kotlin Any to be a nullable type in AOP refdoc examples

When using "Any" as return type, as suggested by the documentation example, in a @Around-Aspect calls to void methods with pjp.proceed() will fail, with a cryptic NullPointerException error:

java.lang.NullPointerException: pjp.proceed() must not be null

I have made an example project to showcase this behavior: spring-aop-docs-bug

Comment From: sdeleuze

Merged with additional similar changes, thanks!