Description of problem:
We are using JenkinsPipelineBuildStrategy in a BuildConfig (as stated at https://docs.openshift.com/container-platform/3.10/dev_guide/builds/build_strategies.html#pipeline-strategy-options).
When starting a pipeline build with some environment variables setting to empty string, the pipeline build fails with the following message found from the console output of the Jenkins pipeline build:

java.lang.IllegalArgumentException: Null value not allowed as an environment variable: NAME

This happens because the Jenkins Sync Plugin (shipped with OpenShift Optimized Jenkins master container image) mistakenly maps the empty environment variable in JenkinsPipelineBuildStrategy into an null value in the Jenkins build parameter. This can be fixed by replacing null values with empty strings.


Version-Release number of selected component (if applicable):
master

How reproducible:


Steps to Reproduce:
1. Create a BuildConfig on OpenShift with JenkinsPipelineBuildStrategy, define some environment variables with empty string:

kind: "BuildConfig"
apiVersion: "v1"
metadata:
  name: "demo-pipeline"
spec:
  strategy:
    jenkinsPipelineStrategy:
      env:
      - name: "NAME"
        value: ""
      jenkinsfile: |-
        pipeline {
          agent {
            kubernetes {
              cloud 'openshift'
              label "jenkins-slave-${UUID.randomUUID().toString()}"
              yaml """
              apiVersion: v1
              kind: Pod
              metadata:
                labels:
                  app: "my-jenkins-slave"
              spec:
                containers:
                - name: jnlp
                  image: docker.io/openshift/jenkins-slave-base-centos7:latest
                  tty: true
                  resources:
                    requests:
                      memory: 512Mi
                      cpu: 200m
                    limits:
                      memory: 768Mi
                      cpu: 500m
              """
            }
          }
          stages {
            stage('foo') {
              steps {
                echo "Hello, ${env.NAME}"
              }
            }
          }
        }
2. start a build with `oc start-build demo-pipeline` or `oc start-build demo-pipeline -e NAME=`
Actual results:

You will get an error message from the Jenkins Console output like this:

java.lang.IllegalArgumentException: Null value not allowed as an environment variable: NAME
	at hudson.EnvVars.put(EnvVars.java:359)
	at hudson.model.StringParameterValue.buildEnvironment(StringParameterValue.java:59)
	at hudson.model.ParametersAction.buildEnvironment(ParametersAction.java:145)
	at hudson.model.Run.getEnvironment(Run.java:2294)
	at org.jenkinsci.plugins.workflow.job.WorkflowRun.getEnvironment(WorkflowRun.java:513)
	at org.csanchez.jenkins.plugins.kubernetes.pipeline.ContainerStepExecution.start(ContainerStepExecution.java:86)
	at org.jenkinsci.plugins.workflow.cps.DSL.invokeStep(DSL.java:229)
	at org.jenkinsci.plugins.workflow.cps.DSL.invokeMethod(DSL.java:153)
	at org.jenkinsci.plugins.workflow.cps.CpsScript.invokeMethod(CpsScript.java:122)
	at org.codehaus.groovy.runtime.callsite.PogoMetaClassSite.call(PogoMetaClassSite.java:48)
	at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:48)
	at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:113)
	at com.cloudbees.groovy.cps.sandbox.DefaultInvoker.methodCall(DefaultInvoker.java:20)
	at org.csanchez.jenkins.plugins.kubernetes.pipeline.KubernetesDeclarativeAgentScript.run(jar:file:/var/lib/jenkins/plugins/kubernetes/WEB-INF/lib/kubernetes.jar!/org/csanchez/jenkins/plugins/kubernetes/pipeline/KubernetesDeclarativeAgentScript.groovy:58)
	at org.jenkinsci.plugins.pipeline.modeldefinition.agent.CheckoutScript.checkoutAndRun(jar:file:/var/lib/jenkins/plugins/pipeline-model-extensions/WEB-INF/lib/pipeline-model-extensions.jar!/org/jenkinsci/plugins/pipeline/modeldefinition/agent/CheckoutScript.groovy:66)
	at org.jenkinsci.plugins.pipeline.modeldefinition.agent.CheckoutScript.doCheckout(jar:file:/var/lib/jenkins/plugins/pipeline-model-extensions/WEB-INF/lib/pipeline-model-extensions.jar!/org/jenkinsci/plugins/pipeline/modeldefinition/agent/CheckoutScript.groovy:42)
	at org.csanchez.jenkins.plugins.kubernetes.pipeline.KubernetesDeclarativeAgentScript.run(jar:file:/var/lib/jenkins/plugins/kubernetes/WEB-INF/lib/kubernetes.jar!/org/csanchez/jenkins/plugins/kubernetes/pipeline/KubernetesDeclarativeAgentScript.groovy:48)
	at ___cps.transform___(Native Method)
	at com.cloudbees.groovy.cps.impl.ContinuationGroup.methodCall(ContinuationGroup.java:57)
	at com.cloudbees.groovy.cps.impl.FunctionCallBlock$ContinuationImpl.dispatchOrArg(FunctionCallBlock.java:109)
	at com.cloudbees.groovy.cps.impl.FunctionCallBlock$ContinuationImpl.fixArg(FunctionCallBlock.java:82)
	at sun.reflect.GeneratedMethodAccessor302.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.ClosureBlock.eval(ClosureBlock.java:46)
	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:122)
	at org.codehaus.groovy.runtime.GroovyCategorySupport.use(GroovyCategorySupport.java:261)
	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$1.run(ContextResettingExecutorService.java:28)
	at java.util.concurrent.Executors$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)
Finished: FAILURE


Expected results:

The pipeline build is successful.

Additional info:
Because this is easy to fix, I've open a PR for this issue https://github.com/openshift/jenkins-sync-plugin/pull/250