Fix a valgrind unit test failure

[cbi42]

Summary: fix the valgrind failure from https://github.com/facebook/rocksdb/actions/runs/11813904728/job/32911902535?fbclid=IwZXh0bgNhZW0CMTEAAR2GJs1U6mNwNv3zwPzU8rpCmBHqfStV3dupj2o_-686RneLKXADaSZH5-U_aem_ADUQy7bzknoseVpjrOc5SQ

[ RUN      ] WBWIMemTableTest.ReadFromWBWIMemtable
==1150870== Conditional jump or move depends on uninitialised value(s)
==1150870==    at 0x50FE67A: rocksdb::WBWIMemTable::Get(rocksdb::LookupKey const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >*, rocksdb::PinnableWideColumns*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >*, rocksdb::Status*, rocksdb::MergeContext*, unsigned long*, unsigned long*, rocksdb::ReadOptions const&, bool, rocksdb::ReadCallback*, bool*, bool) (wbwi_memtable.cc:60)
==1150870==    by 0x50FF92A: rocksdb::WBWIMemTable::MultiGet(rocksdb::ReadOptions const&, rocksdb::MultiGetContext::Range*, rocksdb::ReadCallback*, bool) (wbwi_memtable.cc:120)
==1150870==    by 0x1879EF: rocksdb::WBWIMemTableTest_ReadFromWBWIMemtable_Test::TestBody() (write_batch_with_index_test.cc:3580)

Test plan: valgrind ./write_batch_with_index_test --gtest_filter="*ReadFromWBWIMemtable*"

[facebook-github-bot]

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[facebook-github-bot]

@cbi42 merged this pull request in 9a136e1.