After commit ccd85b57af60d7034db372b9501d059fbc5941e4 I can no longer open my wallet without warnings.

![Screenshot from 2020-05-22 10-45-35](https://user-images.githubusercontent.com/6399679/82679920-9704a180-9c19-11ea-8f55-4c935ced8fe2.png)

```
Warning: Error reading /home/marco/.bitcoin/regtest/wallet.dat! All keys read correctly, but transaction data or address book entries might be missing or incorrect.

{
    static std::atomic<bool> fOneThread(false);
    if (fOneThread.exchange(true)) {
        return;
    }
    if (!gArgs.GetBoolArg("-flushwallet", DEFAULT_FLUSHWALLET)) {
        return;
    }
    for (const std::shared_ptr<CWallet>& pwallet : GetWallets()) {
        WalletDatabase& dbh = pwallet->GetDBHandle();
        unsigned int nUpdateCounter = dbh.nUpdateCounter;
        if (dbh.nLastSeen != nUpdateCounter) {
            dbh.nLastSeen = nUpdateCounter;
            dbh.nLastWalletUpdate = GetTime();
        }
        if (dbh.nLastFlushed != nUpdateCounter && GetTime() - dbh.nLastWalletUpdate >= 2) {
            if (BerkeleyBatch::PeriodicFlush(dbh)) {
                dbh.nLastFlushed = nUpdateCounter;
            }
        }
    }
    fOneThread = false;
}
bool WalletBatch::VerifyEnvironment(const fs::path& wallet_path, bilingual_str& errorStr)