[llvm] [llvm] fix nullptr dereference in BasicBlock::getIrrLoopHeaderWeight (PR #116192)

[Nikita Popov via llvm-commits]

https://github.com/nikic requested changes to this pull request.

Can you please explain why this API should be expected to work with a partially constructed block? I suspect this is trying to paper over an issue elsewhere.

https://github.com/llvm/llvm-project/pull/116192