[llvm] [SelectionDAG] Fix null pointer dereference in resolveDanglingDebugInfo (PR #174341)

[Tom Stellard via llvm-commits]

tstellar wrote:

Hi @MetalOxideSemi,  in the future could you try to write a more concise commit message.  Some things that could be omitted:

* The Summary section is essentially the same as the first line of the message and could be omitted.
* The Solution section is not really adding any useful information.
* You don't need to put the test case in the commit message, it is already in the added files.
* The testing section does not need to list which files have been added, we can see this from the patch diff.
* I don't think the `Related PRs` section is necessary.

https://github.com/llvm/llvm-project/pull/174341