salvage wallet warns "Number of keys in data does not match number of values" on uncorrupt wallet file

```
Salvage: WARNING: Number of keys in data does not match number of values.
Salvage: WARNING: Unexpected end of file while reading salvage output.
WARNING: WalletBatch::Recover skipping key: CDataStream::read(): end of data: iostream error
```

Steps to reproduce: #19078 

The failure happens intermittently.