Fix memory leak (#2475)

### What problem does this PR solve?

Fix memory leak in IVFIndexInMem

Fix #2465

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

src/storage/knn_index/knn_ivf/ivf_index_data_in_mem.cpp

@@ -111,6 +111,7 @@ class IVFIndexInMemT final : public IVFIndexInMem {
     }
 
     ~IVFIndexInMemT() {
+        std::unique_lock lock(rw_mutex_);
         if (own_ivf_index_storage_) {
             DecreaseMemoryUsageBase(MemoryUsed());
         }
@@ -237,6 +238,7 @@ class IVFIndexInMemT final : public IVFIndexInMem {
         BufferHandle handle = new_chunk_index_entry->GetIndex();
         auto *data_ptr = static_cast<IVFIndexInChunk *>(handle.GetDataMut());
         data_ptr->GetMemData(std::move(*ivf_index_storage_));
+        delete ivf_index_storage_;
         ivf_index_storage_ = data_ptr->GetIVFIndexStoragePtr();
         own_ivf_index_storage_ = false;
         dump_handle_ = std::move(handle);