Allow Kotlin method invocation type to be considered valid if null

[greg-dennis]

What's changed?

This allows the type of a Kotlin MethodInvocation to be considered valid if null, as already anticipated by the by the KotlinTreeParseVisitor.

What's your motivation?

• Fix/workaround for https://github.com/openrewrite/rewrite/issues/6408

Anything in particular you'd like reviewers to focus on?

Anyone you would like to review specifically?

@timtebeek has context from Slack

Have you considered any alternatives or workarounds?

I tried to find a way to force the parser to resolve the type, but the issue appears to be deep in the bowels of the Jetbrains FIR.

Any additional context

Checklist

• [x] I've added unit tests to cover both positive and negative cases
• [x] I've read and applied the recipe conventions and best practices
• [x] I've used the IntelliJ IDEA auto-formatter on affected files