[clang] [Clang][Sema] fix outline member function template with default align crash (PR #78400)

[Erich Keane via cfe-commits]

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@@ -859,6 +859,9 @@ Bug Fixes in This Version
   Fixes (`#78290 <https://github.com/llvm/llvm-project/issues/78290>`_)
 - Fixed assertion failure with deleted overloaded unary operators.
   Fixes (`#78314 <https://github.com/llvm/llvm-project/issues/78314>`_)
+- Fix crash when specialize out-of-line member function with default parameter
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erichkeane wrote:

```suggestion
- Fix a crash when specializing an out-of-line member function with a default parameter where we did an incorrect specialization of the initialization of the default parameter.
```

Is this accurate?  

https://github.com/llvm/llvm-project/pull/78400