[clang] [-Wcompletion-handler] Fix a non-termination issue (PR #78380)

[Valeriy Savchenko via cfe-commits]

https://github.com/SavchenkoValeriy approved this pull request.

Awesome! Thank you for fixing the problem and for describing it so in detail. 

https://github.com/llvm/llvm-project/pull/78380