[clang] [clang-tools-extra] [clang][AST] Fix crash in MatchChildASTVisitor::TraverseLambdaExpr (PR #70962)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

> * @AaronBallman Having a nullptr init capture seems fishy, do we actually mean to allow capturing vla by reference here?

That does seem fishy to me -- I would expect VLA to behave the same as a constant-size array in terms of what we capture. So I think we do want to capture the VLA by reference (that's how we behave for constant-sized arrays).

https://github.com/llvm/llvm-project/pull/70962