[llvm] [ADT] Fix a minor build error (PR #104840)

[Jakub Kuderski via llvm-commits]

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@@ -316,7 +316,7 @@ TEST(UniqueFunctionTest, InlineStorageWorks) {
   // We do assume a couple of implementation details of the unique_function here:
   //  - It can store certain small-enough payload inline
   //  - Inline storage size is at least >= sizeof(void*)
-  void *ptr;
+  void *ptr = nullptr;
   unique_function<void(void *)> UniqueFunctionWithInlineStorage{
       [ptr](void *self) {
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kuhar wrote:

address of a reference is the underlying pointer

https://github.com/llvm/llvm-project/pull/104840