[clang] [clang] Fix crash on implicit conversion of a reference NTTP bound to a subobject (PR #215900)

[Nico Weber via cfe-commits]

nico wrote:

Thanks: Patch lgtm too and I merged it.

Given the somewhat wordy comment and PR description, I'd like to make sure you've seen https://llvm.org/docs/AIToolPolicy.html, especially the "Contributors are expected to be transparent and label contributions that contain substantial amounts of tool-generated content." bit 🙂

https://github.com/llvm/llvm-project/pull/215900