[clang] [Sema] Fix crash on invalid operator template-id (PR #181404)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `arc-builder` running on `arc-worker` while building `clang` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/3/builds/29334

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

```
Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'Clang :: SemaCXX/crash-invalid-operator-template.cpp' FAILED ********************
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 1
/buildbot/worker/arc-folder/build/bin/clang -cc1 -internal-isystem /buildbot/worker/arc-folder/build/lib/clang/23/include -nostdsysteminc -fsyntax-only -verify /buildbot/worker/arc-folder/llvm-project/clang/test/SemaCXX/crash-invalid-operator-template.cpp
# executed command: /buildbot/worker/arc-folder/build/bin/clang -cc1 -internal-isystem /buildbot/worker/arc-folder/build/lib/clang/23/include -nostdsysteminc -fsyntax-only -verify /buildbot/worker/arc-folder/llvm-project/clang/test/SemaCXX/crash-invalid-operator-template.cpp
# .---command stderr------------
# | error: 'expected-error' diagnostics expected but not seen: 
# |   File /buildbot/worker/arc-folder/llvm-project/clang/test/SemaCXX/crash-invalid-operator-template.cpp Line 3 (directive at /buildbot/worker/arc-folder/llvm-project/clang/test/SemaCXX/crash-invalid-operator-template.cpp:5): type specifier is required
# |   File /buildbot/worker/arc-folder/llvm-project/clang/test/SemaCXX/crash-invalid-operator-template.cpp Line 3 (directive at /buildbot/worker/arc-folder/llvm-project/clang/test/SemaCXX/crash-invalid-operator-template.cpp:6): typedef name must be an identifier
# | error: 'expected-error' diagnostics seen but not expected: 
# |   File /buildbot/worker/arc-folder/llvm-project/clang/test/SemaCXX/crash-invalid-operator-template.cpp Line 3: declarator requires an identifier
# | 3 errors generated.
# `-----------------------------
# error: command failed with exit status: 1

--

********************


```

</details>

https://github.com/llvm/llvm-project/pull/181404