[clang] [clang] Fix possible nullptr deref in BuildCXXNestedNameSpecifier (PR #166995)

[Paul Kirth via cfe-commits]

================
@@ -0,0 +1,7 @@
+// RUN: %clang_cc1 -fsyntax-only %s -verify
+namespace a {
+template <class b>
+void c() {
+  ((::c::)); // expected-error {{expected unqualified-id}}
----------------
ilovepi wrote:

@efriedma-quic does the new version work the way you'd expect it to? I'd like to get this merged if it does.

https://github.com/llvm/llvm-project/pull/166995