GH-3697: DelegatingInvocableHandler.invoke() returning null

[ivamly]

Fixes: #3697

Change the logic in the DelegatingInvocableHandler.invoke()

[sobychacko]

@ivamly Thanks for the PR. There are checkstyle issues in the PR. Please run a full build from the PR branch - .gradlew check. Also, you need to add your name as an author to the class you modified. Finally, see this blog for DCO based commits - https://spring.io/blog/2025/01/06/hello-dco-goodbye-cla-simplifying-contributions-to-spring. You need to modify the commit message based on that information.

[ivamly]

Thank for the help! I'll do it

[sobychacko]

@ivamly Even though it was merged, I realized that this change needs to wait until we break into the new version (4.0.x). We cannot put this in the current versions since it is a breaking change. Sorry about the confusion. @artembilan made that clear in the original description. I will reopen your PR, and then we can tackle this once we branch off into 4.0.x.

[sobychacko]

Actually, i cannot reopen this PR since it was already merged, and we had to back it out. Can you issue another PR based on your latest changes? You can also wait until we branch into the 4.0.x version. Thanks!