[clang-tools-extra] [clangd] Fix crash on completion with out-of-range position (PR #196112)

[Krzysztof Jędruczyk via cfe-commits]

kjedruczyk wrote:

Thanks for the review @ArcsinX. If you could, please, merge it it would be great - I don't have the access.

https://github.com/llvm/llvm-project/pull/196112