bugfix npe monitor jobid may be null

[tomsun28]

What's changed?

java.lang.NullPointerException: Cannot invoke "Object.hashCode()" because "key" is null
    at java.base/java.util.concurrent.ConcurrentHashMap.replaceNode(ConcurrentHashMap.java:1111)
    at java.base/java.util.concurrent.ConcurrentHashMap.remove(ConcurrentHashMap.java:1102)
    at java.base/java.util.concurrent.ConcurrentHashMap$KeySetView.remove(ConcurrentHashMap.java:4626)
    at org.dromara.hertzbeat.manager.scheduler.CollectorAndJobScheduler.cancelAsyncCollectJob(CollectorAndJobScheduler.java:431)
    at org.dromara.hertzbeat.manager.service.impl.MonitorServiceImpl.deleteMonitors(MonitorServiceImpl.java:600)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:568)
    at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:351)

Checklist

• I hereby agree to the terms of the HertzBeat CLA
• I have read the Contributing Guide
• I have written the necessary doc or comment.
• I have added the necessary unit tests and all cases have passed.

Add or update API

• I have added the necessary e2e tests and all cases have passed.

[zqr10159]

lgtm