fix: exeucte_job_plan API，全局变量-主机传入空的主机列表，报系统内部错误

[wangyu096]

Version / Branch / tag

3.7.x

出了什么问题？(What Happened?)

exeucte_job_plan API，全局变量-主机传入空的主机列表，报系统内部错误

[2023-06-12 15:54:28.303] ERROR [job-execute,6e0865f60abf5735e7c43c019f3e4094,d799f78d616dc9b9] 26969 --- [http-nio-10502-exec-112] b.j.c.w.e.h.EsbExceptionControllerAdvice : Handle exception

java.lang.NullPointerException: null
	at com.tencent.bk.job.execute.service.impl.TaskExecuteServiceImpl.lambda$extractHosts$26(TaskExecuteServiceImpl.java:1102)
	at java.util.HashMap$Values.forEach(HashMap.java:981)
	at com.tencent.bk.job.execute.service.impl.TaskExecuteServiceImpl.extractHosts(TaskExecuteServiceImpl.java:1100)
	at com.tencent.bk.job.execute.service.impl.TaskExecuteServiceImpl.acquireAndSetHosts(TaskExecuteServiceImpl.java:683)
	at com.tencent.bk.job.execute.service.impl.TaskExecuteServiceImpl.executeJobPlan(TaskExecuteServiceImpl.java:1223)
	at com.tencent.bk.job.execute.api.esb.v3.EsbExecuteJobPlanV3ResourceImpl.executeJobPlan(EsbExecuteJobPlanV3ResourceImpl.java:105)
	at com.tencent.bk.job.execute.api.esb.v3.EsbExecuteJobPlanV3ResourceImpl$$FastClassBySpringCGLIB$$4834dbc6.invoke(<generated>)
	at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:218)
	at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:793)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163)
	at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:763)
	at org.springframework.aop.aspectj.MethodInvocationProceedingJoinPoint.proceed(MethodInvocationProceedingJoinPoint.java:89)
	at com.tencent.bk.job.common.esb.metrics.EsbApiTimedAspect.processWithTimer(EsbApiTimedAspect.java:92)
	at com.tencent.bk.job.common.esb.metrics.EsbApiTimedAspect.timedMethod(EsbApiTimedAspect.java:83)
	at sun.reflect.GeneratedMethodAccessor338.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)

如何复现？(How to reproduce?)

见问题描述

预期结果(What you expect?)
传入空的主机列表，如果这个全局变量本身没有被执行方案引用，那么不需要报错

[wangyu096]

问题分析：处理没有主机列表的全局变量-主机类型空指针报错，需要添加前置验证