[heap] Initialize invalidated_slots_[OLD_TO_SHARED]

While this field isn't used, inititialize it to null.

Bug: v8:11708
Change-Id: I9698e73183f49ef54b8978383e1406e5cf765c75
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3562982
Auto-Submit: Dominik Inführ <dinfuehr@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79710}

src/heap/memory-chunk.cc

@@ -138,6 +138,7 @@ MemoryChunk::MemoryChunk(Heap* heap, BaseSpace* space, size_t chunk_size,
                                        nullptr);
   invalidated_slots_[OLD_TO_NEW] = nullptr;
   invalidated_slots_[OLD_TO_OLD] = nullptr;
+  invalidated_slots_[OLD_TO_SHARED] = nullptr;
   if (V8_EXTERNAL_CODE_SPACE_BOOL) {
     // Not actually used but initialize anyway for predictability.
     invalidated_slots_[OLD_TO_CODE] = nullptr;