values smaller than 0.001 sat/B can't be represented by CFeeRate, but they are not rejected.

```
./src/bitcoin-cli -named sendtoaddress address=bcrt1qwkmhqum095zau5rf2velq55cq938vrd7uw8m4r amount=1.23 fee_rate=0.0009

error code: -6
error message:
Fee rate (0.000 sat/vB) is lower than the minimum fee rate setting (1.000 sat/vB)
```

```
./src/bitcoin-cli -named sendtoaddress address=bcrt1qwkmhqum095zau5rf2velq55cq938vrd7uw8m4r amount=1.23 fee_rate=0.000000000009

error code: -3
error message:
Invalid amount

std::string strMessage = request.params[1].get_str();
    CTxDestination dest = DecodeDestination(strAddress);
    if (!IsValidDestination(dest)) {
        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Invalid address");
    }
    const PKHash* pkhash = std::get_if<PKHash>(&dest);
    if (!pkhash) {
        throw JSONRPCError(RPC_TYPE_ERROR, "Address does not refer to key");
    }
    std::string signature;
    SigningResult err = pwallet->SignMessage(strMessage, *pkhash, signature);
    if (err == SigningResult::SIGNING_FAILED) {
        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, SigningResultString(err));
    } else if (err != SigningResult::OK){
        throw JSONRPCError(RPC_WALLET_ERROR, SigningResultString(err));
    }
    return signature;
},
    };
}
static CAmount GetReceived(const CWallet& wallet, const UniValue& params, bool by_label) EXCLUSIVE_LOCKS_REQUIRED(wallet.cs_wallet)
{
    std::set<CTxDestination> address_set;
    if (by_label) {
        
        std::string label = LabelFromValue(params[0]);
        address_set = wallet.GetLabelAddresses(label);
    } else {
        
        CTxDestination dest = DecodeDestination(params[0].get_str());