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.
{
        SetTx(MakeTransactionRef());
        Init();
    }
    explicit CMerkleTx(CTransactionRef arg)
    {
        SetTx(std::move(arg));
        Init();
    }
    /** Helper conversion operator to allow passing CMerkleTx where CTransaction is expected.
     *  TODO: adapt callers and remove this operator. */
    operator const CTransaction&() const { return *tx; }
    void Init()
    {
        hashBlock = uint256();
        nIndex = -1;
    }
    void SetTx(CTransactionRef arg)
    {
        tx = std::move(arg);
    }
    ADD_SERIALIZE_METHODS;
    template <typename Stream, typename Operation>
    inline void SerializationOp(Stream& s, Operation ser_action) {