@achow101 noted we don't reject them therefore they must be silently accepted. This is not part of the specs, we should remove them. Also cc @sipa.

I can take care of this.
KeyPath end_path;
        for (; k < (int)m_path.size(); ++k) {
            end_path.push_back(m_path.at(k));
        }
        
        CKeyID id = m_root_extkey.pubkey.GetID();
        std::copy(id.begin(), id.begin() + 4, origin.fingerprint);
        CExtPubKey xpub;
        CExtKey lh_xprv;
        
        if (cache != nullptr) {
            cache->GetCachedLastHardenedExtPubKey(m_expr_index, xpub);
        }
        if (!xpub.pubkey.IsValid()) {
            
            CExtKey xprv;
            if (!GetDerivedExtKey(arg, xprv, lh_xprv)) return false;
            xpub = lh_xprv.Neuter();
        }
        assert(xpub.pubkey.IsValid());
        
        std::string origin_str = HexStr(origin.fingerprint) + FormatHDKeypath(origin.path);
        out = "[" + origin_str + "]" + EncodeExtPubKey(xpub) + FormatHDKeypath(end_path);
        if (IsRange()) {
            out += "/*";
            assert(m_derive == DeriveType::UNHARDENED);
        }
        return true;
    }
    bool GetPrivKey(int pos, const SigningProvider& arg, CKey& key) const override