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

{
    if (URL_DECODE && request.URI.substr(0, WALLET_ENDPOINT_BASE.size()) == WALLET_ENDPOINT_BASE) {
        
        wallet_name = URL_DECODE(request.URI.substr(WALLET_ENDPOINT_BASE.size()));
        return true;
    }
    return false;
}
std::shared_ptr<CWallet> GetWalletForJSONRPCRequest(const JSONRPCRequest& request)
{
    CHECK_NONFATAL(request.mode == JSONRPCRequest::EXECUTE);
    std::string wallet_name;
    if (GetWalletNameFromJSONRPCRequest(request, wallet_name)) {
        std::shared_ptr<CWallet> pwallet = GetWallet(wallet_name);
        if (!pwallet) throw JSONRPCError(RPC_WALLET_NOT_FOUND, "Requested wallet does not exist or is not loaded");
        return pwallet;
    }
    std::vector<std::shared_ptr<CWallet>> wallets = GetWallets();
    if (wallets.size() == 1) {
        return wallets[0];
    }
    if (wallets.empty()) {
        throw JSONRPCError(
            RPC_WALLET_NOT_FOUND, "No wallet is loaded. Load a wallet using loadwallet or create a new one with createwallet. (Note: A default wallet is no longer automatically created)");
    }
    throw JSONRPCError(RPC_WALLET_NOT_SPECIFIED,
        "Wallet file not specified (must request wallet RPC through /wallet/<filename> uri-path).");
}
void EnsureWalletIsUnlocked(const CWallet& wallet)