stratum: parse_notify(): Don't die on malformed bbversion/prev_hash/nbit/ntime.

Might have introduced a memory leak, don't have time to check. :(

Should the other hex2bin()'s be checked?

Thanks to Mick Ayzenberg <mick.dejavusecurity.com> for finding this.
static void set_nettime(void)
{
	wr_lock(&netacc_lock);
	cgtime(&nettime);
	wr_unlock(&netacc_lock);
}

static void set_nettime(void)
{
	wr_lock(&netacc_lock);
	cgtime(&nettime);
	wr_unlock(&netacc_lock);
}
