add: _tag->s = 0;
context: get_to_tag(struct sip_msg* _m, str* _tag){	if (!_m->to) {		LOG(L_ERR, "get_to_tag(): To header field missing\n");		return -1;	}	if (get_to(_m)->tag_value.len) {		_tag->s = get_to(_m)->tag_value.s;		_tag->len = get_to(_m)->tag_value.len;	} else {		_tag->len = 0;	}	return 0;}