@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.
final_extkey = xprv.Neuter();
            if (lh_xprv.key.IsValid()) {
                last_hardened_extkey = lh_xprv.Neuter();
            }
        } else {
            for (auto entry : m_path) {
                if (!parent_extkey.Derive(parent_extkey, entry)) return false;
            }
            final_extkey = parent_extkey;
            if (m_derive == DeriveType::UNHARDENED) der = parent_extkey.Derive(final_extkey, pos);
            assert(m_derive != DeriveType::HARDENED);
        }
        if (!der) return false;
        final_info_out = final_info_out_tmp;
        key_out = final_extkey.pubkey;
        if (write_cache) {
            
            if (m_derive != DeriveType::HARDENED) {
                write_cache->CacheParentExtPubKey(m_expr_index, parent_extkey);
                
                if (last_hardened_extkey.pubkey.IsValid()) {
                    write_cache->CacheLastHardenedExtPubKey(m_expr_index, last_hardened_extkey);
                }
            } else if (final_info_out.path.size() > 0) {
                write_cache->CacheDerivedExtPubKey(m_expr_index, pos, final_extkey);
            }
        }
        return true;
    }
    std::string ToString(StringType type, bool normalized) const