The efforts around SPR-15540 and SPR-15720 have uncovered minor issues like missing null handling and/or missing assertions in quite a few places. Let's selectively backport some of those refinements to 4.3.x along with 5.0 GA.
is related to
SPR-16123SpelExpression throws NullPointerException instead of EvaluationException for primitives
SPR-16075setArguments(null) on MethodInvoker no longer coerces null to Object
SPR-15540Introduce null-safety of Spring Framework API