for(int i = 0; i < 15; i++) {
    build job: 'test_job', quietPeriod: 0, wait: false
}

node {
 println "DOWNSTREAM JOB"
}

Started by upstream project "test_parent" build number 19
originally caused by:
 Started by user Anshu Arya
Running: Allocate node : Start
Running on master in /var/lib/jenkins/workspace/test_job@8
Running: Allocate node : Body : Start
Running: Loaded script: /jenkins_scripts/test_job.groovy
Running: Evaluate a Groovy source file into the workflow script : Body : Start
Running: Allocate node : Start
Running on master in /var/lib/jenkins/workspace/test_job@2
Running: Allocate node : Body : Start
Running: Print Message
DOWNSTREAM JOB
Running: Allocate node : Body : End
Running: Allocate node : End
Running: Evaluate a Groovy source file into the workflow script : Body : End
Running: Allocate node : Body : End
Running: Allocate node : End
Running: End of Workflow
java.lang.NullPointerException
	at org.jenkinsci.plugins.workflow.support.steps.ExecutorStepExecution$PlaceholderTask.finish(ExecutorStepExecution.java:339)
	at org.jenkinsci.plugins.workflow.support.steps.ExecutorStepExecution$PlaceholderTask.access$400(ExecutorStepExecution.java:144)
	at org.jenkinsci.plugins.workflow.support.steps.ExecutorStepExecution$PlaceholderTask$Callback.finished(ExecutorStepExecution.java:370)
	at org.jenkinsci.plugins.workflow.steps.BodyExecutionCallback$TailCall.onSuccess(BodyExecutionCallback.java:114)
	at org.jenkinsci.plugins.workflow.cps.CpsBodyExecution$SuccessAdapter.receive(CpsBodyExecution.java:311)
	at com.cloudbees.groovy.cps.impl.ContinuationGroup.methodCall(ContinuationGroup.java:71)
	at com.cloudbees.groovy.cps.impl.FunctionCallBlock$ContinuationImpl.dispatchOrArg(FunctionCallBlock.java:106)
	at com.cloudbees.groovy.cps.impl.FunctionCallBlock$ContinuationImpl.fixArg(FunctionCallBlock.java:79)
	at sun.reflect.GeneratedMethodAccessor433.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:497)
	at com.cloudbees.groovy.cps.impl.ContinuationPtr$ContinuationImpl.receive(ContinuationPtr.java:72)
	at com.cloudbees.groovy.cps.impl.ConstantBlock.eval(ConstantBlock.java:21)
	at com.cloudbees.groovy.cps.Next.step(Next.java:58)
	at com.cloudbees.groovy.cps.Continuable.run0(Continuable.java:145)
	at org.jenkinsci.plugins.workflow.cps.CpsThread.runNextChunk(CpsThread.java:164)
	at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup.run(CpsThreadGroup.java:271)
	at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup.access$000(CpsThreadGroup.java:71)
	at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$2.call(CpsThreadGroup.java:180)
	at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$2.call(CpsThreadGroup.java:178)
	at org.jenkinsci.plugins.workflow.cps.CpsVmExecutorService$2.call(CpsVmExecutorService.java:47)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at hudson.remoting.SingleLaneExecutorService$1.run(SingleLaneExecutorService.java:112)
	at jenkins.util.ContextResettingExecutorService$1.run(ContextResettingExecutorService.java:28)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at java.lang.Thread.run(Thread.java:745)
Finished: FAILURE