Built against `master` branch 801dd40666d1e6009920ad3ff755c7bb993b2a62:

If I have no wallet.dat file and run:

    bitcoind -usehd=0

A new wallet.dat file is created and an HD seed is assigned.

I see an error message in the source:

    "Error loading %s: You can't disable HD on an already existing HD wallet or create new non-HD wallets."

but that doesn't get shown because `fFirstRun` is true, and so the code which checks for `-usehd` values doesn't run.

If it's no longer possible to create non-HD wallets, specifying -usehd=0 when creating a wallet should be an error, and not get silently ignored.
int& nChangePosInOut, std::string& strFailReason, const CCoinControl& coin_control, bool sign)
{
    CAmount nValue = 0;
    int nChangePosRequest = nChangePosInOut;
    unsigned int nSubtractFeeFromAmount = 0;
    for (const auto& recipient : vecSend)
    {
        if (nValue < 0 || recipient.nAmount < 0)
        {
            strFailReason = _("Transaction amounts must not be negative");
            return false;
        }
        nValue += recipient.nAmount;
        if (recipient.fSubtractFeeFromAmount)
            nSubtractFeeFromAmount++;
    }
    if (vecSend.empty())
    {
        strFailReason = _("Transaction must have at least one recipient");
        return false;