Bug - _sendEmailNotification may raise groovy.lang.MissingPropertyException: No such property: user for class:

[jackjia-ibm]

If the stage is aborted with timeout, the pipeline will show an exception:

groovy.lang.MissingPropertyException: No such property: user for class: org.jenkinsci.plugins.workflow.steps.TimeoutStepExecution$ExceededTimeout
	at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.unwrap(ScriptBytecodeAdapter.java:53)
	at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.getProperty(ScriptBytecodeAdapter.java:458)
	at com.cloudbees.groovy.cps.sandbox.DefaultInvoker.getProperty(DefaultInvoker.java:39)
	at com.cloudbees.groovy.cps.impl.PropertyAccessBlock.rawGet(PropertyAccessBlock.java:20)
	at org.zowe.jenkins_shared_library.pipelines.base.Pipeline._sendEmailNotification(file:/var/jenkins_home/jobs/zowe-install-test/branches/new-install-script-version/builds/79/libs/jenkins-library/src/org/zowe/jenkins_shared_library/pipelines/base/Pipeline.groovy:852)
	at org.zowe.jenkins_shared_library.pipelines.base.Pipeline.endBase(file:/var/jenkins_home/jobs/zowe-install-test/branches/new-install-script-version/builds/79/libs/jenkins-library/src/org/zowe/jenkins_shared_library/pipelines/base/Pipeline.groovy:770)
	at org.zowe.jenkins_shared_library.pipelines.base.Pipeline.endBase(file:/var/jenkins_home/jobs/zowe-install-test/branches/new-install-script-version/builds/79/libs/jenkins-library/src/org/zowe/jenkins_shared_library/pipelines/base/Pipeline.groovy:784)
	at org.zowe.jenkins_shared_library.pipelines.generic.GenericPipeline.endGeneric(file:/var/jenkins_home/jobs/zowe-install-test/branches/new-install-script-version/builds/79/libs/jenkins-library/src/org/zowe/jenkins_shared_library/pipelines/generic/GenericPipeline.groovy:648)
	at org.zowe.jenkins_shared_library.pipelines.generic.GenericPipeline.end(file:/var/jenkins_home/jobs/zowe-install-test/branches/new-install-script-version/builds/79/libs/jenkins-library/src/org/zowe/jenkins_shared_library/pipelines/generic/GenericPipeline.groovy:657)
	at WorkflowScript.run(WorkflowScript:592)
	at ___cps.transform___(Native Method)
	at com.cloudbees.groovy.cps.impl.PropertyishBlock$ContinuationImpl.get(PropertyishBlock.java:74)
	at com.cloudbees.groovy.cps.LValueBlock$GetAdapter.receive(LValueBlock.java:30)
	at com.cloudbees.groovy.cps.impl.PropertyishBlock$ContinuationImpl.fixName(PropertyishBlock.java:66)
	at sun.reflect.GeneratedMethodAccessor72.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	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:83)
	at com.cloudbees.groovy.cps.Continuable$1.call(Continuable.java:174)
	at com.cloudbees.groovy.cps.Continuable$1.call(Continuable.java:163)
	at org.codehaus.groovy.runtime.GroovyCategorySupport$ThreadCategoryInfo.use(GroovyCategorySupport.java:129)
	at org.codehaus.groovy.runtime.GroovyCategorySupport.use(GroovyCategorySupport.java:268)
	at com.cloudbees.groovy.cps.Continuable.run0(Continuable.java:163)
	at org.jenkinsci.plugins.workflow.cps.SandboxContinuable.access$101(SandboxContinuable.java:34)
	at org.jenkinsci.plugins.workflow.cps.SandboxContinuable.lambda$run0$0(SandboxContinuable.java:59)
	at org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.GroovySandbox.runInSandbox(GroovySandbox.java:108)
	at org.jenkinsci.plugins.workflow.cps.SandboxContinuable.run0(SandboxContinuable.java:58)
	at org.jenkinsci.plugins.workflow.cps.CpsThread.runNextChunk(CpsThread.java:174)
	at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup.run(CpsThreadGroup.java:332)
	at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup.access$200(CpsThreadGroup.java:83)
	at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$2.call(CpsThreadGroup.java:244)
	at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$2.call(CpsThreadGroup.java:232)
	at org.jenkinsci.plugins.workflow.cps.CpsVmExecutorService$2.call(CpsVmExecutorService.java:64)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at hudson.remoting.SingleLaneExecutorService$1.run(SingleLaneExecutorService.java:131)
	at jenkins.util.ContextResettingExecutorService$1.run(ContextResettingExecutorService.java:28)
	at jenkins.security.ImpersonatingExecutorService$1.run(ImpersonatingExecutorService.java:59)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)

The line with error is src/org/zowe/jenkins_shared_library/pipelines/base/Pipeline.groovy:

            if (buildStatus == "ABORTED") {
                emailText = "Aborted by ${((FlowInterruptedException) firstFailingStage.exception).causes[0]?.user}"
            } else {