Spring Ensure varargs component type for MethodHandle is not null in SpEL's ReflectionHelper

The TypeDescriptor for the varargs component type can currently be null in SpEL's ReflectionHelper.convertAllMethodHandleArguments(...) method; however, that should not be possible.

Whereas, in compareArgumentsVarargs(...) and convertArguments(...) the varargs component type can never be null.

My assumption is that we are using an incorrect combination of Class, ResolvableType, and TypeDescriptor in convertAllMethodHandleArguments(...).

I discovered this while working on related SpEL issues and added the following TODO which this issue aims to address.

https://github.com/spring-projects/spring-framework/blob/4de2aadf723234992eccee0ada7d9b5e3be6a488/spring-expression/src/main/java/org/springframework/expression/spel/support/ReflectionHelper.java#L386-L387