[clang] [clang-format] Fix a crash in formatting unbalanced angle brackets (PR #173456)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `ppc64le-flang-rhel-clang` running on `ppc64le-flang-rhel-test` while building `clang` at step 3 "clean-build-dir".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/157/builds/43265

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 3 (clean-build-dir) failure: Delete failed. (failure) (timed out)
Step 4 (cmake-configure) failure: cmake (failure) (timed out)

```

</details>

https://github.com/llvm/llvm-project/pull/173456