修改以下代码，使其(SELECT EndTime FROM Alarm_GK WHERE id = 350570)的值为空时，不执行这条and c.AlarmTime < (SELECT EndTime FROM Alarm_GK WHERE id = 350570)判断语句

以下是修改后的代码：

SELECT a.ID, a.AlarmTime, a.Message
FROM Alarm_GK a
JOIN Device_GK b ON a.DeviceID = b.ID
WHERE a.DeviceID = 1
AND a.AlarmTime > '2022-01-01'
AND (
    (SELECT EndTime FROM Alarm_GK WHERE id = 350570) IS NULL 
    OR a.AlarmTime < (SELECT EndTime FROM Alarm_GK WHERE id = 350570)
)

修改后，当 `(SELECT EndTime FROM Alarm_GK WHERE id = 350570)` 的值为空时，判断语句 `AND a.AlarmTime < (SELECT EndTime FROM Alarm_GK WHERE id = 350570)` 将不会执行，从而避免了错误。