This is to track the regression introduced in master, which needs fixing for 0.14. See #9240, #9371, etc.
{
    nIndex = -1;
    keypool.vchPubKey = CPubKey();
    {
        LOCK(cs_wallet);
        if (!IsLocked())
            TopUpKeyPool();
        
        if(setKeyPool.empty())
            return;
        CWalletDB walletdb(strWalletFile);
        nIndex = *(setKeyPool.begin());
        setKeyPool.erase(setKeyPool.begin());
        if (!walletdb.ReadPool(nIndex, keypool))
            throw runtime_error(std::string(__func__) + ": read failed");
        if (!HaveKey(keypool.vchPubKey.GetID()))
            throw runtime_error(std::string(__func__) + ": unknown key in key pool");
        assert(keypool.vchPubKey.IsValid());
        LogPrintf("keypool reserve %d\n", nIndex);
    }
}
void CWallet::KeepKey(int64_t nIndex)