Backport fix for clangd#1743 to 17.x branch

[HighCommander4]

I would like to propose backporting the fix for clangd/clangd#1743 to the 17.x branch.

This fix is low risk (it's just adding a null pointer check), and it fixes a clangd crash.

[HighCommander4]

/cherry-pick 1994e11

[llvmbot]

/branch llvm/llvm-project-release-prs/issue72621

[llvmbot]

/pull-request llvm/llvm-project-release-prs#779

[llvmbot]

@llvm/issue-subscribers-clangd

Author: Nathan Ridge (HighCommander4)

I would like to propose backporting the fix for https://github.com/clangd/clangd/issues/1743 to the 17.x branch.

This fix is low risk (it's just adding a null pointer check), and it fixes a clangd crash.