[clang-tidy] Fix crash in `modernize-use-default-member-init`

This was causes by `getValueOfValueInit` unconditionally calling
`getScalarTypeKind` on the member type, which would then trigger an
assertions since arrays are not scalar type.

This fixes llvm#63285

Reviewed By: PiotrZSL

Differential Revision: https://reviews.llvm.org/D152802