[clang] Fix null-deref thanks to an attribute on a global declarator chunk (PR #83611)

[Aaron Ballman via cfe-commits]

================
@@ -734,6 +735,9 @@ class AttributePool {
     pool.Attrs.clear();
   }
 
+  /// Take a list of attributes from another pool and add them to this pool.
----------------
AaronBallman wrote:

```suggestion
  /// Removes the attributes from \c List, which are owned by \c Pool, and adds them at the end
  /// of this \c AttributePool.
```

https://github.com/llvm/llvm-project/pull/83611