[llvm] [ctx_prof] Handle case when no root is in this Module. (PR #107463)

[Mircea Trofin via llvm-commits]

mtrofin wrote:

### Merge activity

* **Sep 6, 4:40 PM EDT**: @mtrofin started a stack merge that includes this pull request via [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/107463).


https://github.com/llvm/llvm-project/pull/107463