[clang] [clang][analyzer] CallAndMessage warnings at pointer to uninitialized struct (PR #164600)

[Donát Nagy via cfe-commits]

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

The change looks good to me.

I think the message formatting could be simplified by using `llvm::formatv` instead of the more verbose `raw_ostream` handling (as I write in inline comments), but the current implementation is also correct.

https://github.com/llvm/llvm-project/pull/164600