Improved getting job builds function

Change-Id: Icae1d9a32e9fffa19c60d5c9a5e69d61cd16f715
diff --git a/src/com/mirantis/mk/JenkinsUtils.groovy b/src/com/mirantis/mk/JenkinsUtils.groovy
index f86b423..ef6ce0c 100644
--- a/src/com/mirantis/mk/JenkinsUtils.groovy
+++ b/src/com/mirantis/mk/JenkinsUtils.groovy
@@ -11,6 +11,11 @@
  * @param jobName job name
  * @return list of running builds
  */
+@NonCPS
 def getJobRunningBuilds(jobName){
-  return Jenkins.instance.items.find{it -> it.name.equals(jobName)}.builds.findAll{build -> build.isBuilding()}
+  def job = Jenkins.instance.items.find{it -> it.name.equals(jobName)}
+  if(job){
+   return job.builds.findAll{build -> build.isBuilding()}
+  }
+  return []
 }
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