Fix #5401 Single-arg method invocations should not fall back to input…

[JoostK]

… argument for null return values

Fixes #5401

[cowtowncoder]

Makes sense, but I am puzzled by original code -- why is it returning argument instead of null... :-/

@stevenschlansker Any idea on ^^^?

[stevenschlansker]

Sorry, I'm not sure. Seems good to remove to me.

[cowtowncoder]

@stevenschlansker All good -- did not mean as in "WTH" but more like "is this safe to remove" :)
So sanity check so we won't remove something important.

[cowtowncoder]

So, looks good, thank you @JoostK !

Just one thing before I merge (and back-port in 3.0(.3)) -- unless we have one already, need CLA from here:

https://github.com/FasterXML/jackson/blob/main/contributor-agreement.pdf

Only needs to be sent once, good for all future contributions.
The usual way is to print, fill & sign, scan/photo, email to cla at fasterxml dot com.

Once we have it, I can merge this in. Thanks again!

[JoostK]

Only needs to be sent once, good for all future contributions. The usual way is to print, fill & sign, scan/photo, email to cla at fasterxml dot com.

Done

[cowtowncoder]

Merged in, backported in 3.0 for 3.0.3 release