Conditionally execute Coverity plugin fails during publish.

Had a project with Coverity plugin installed and configured, successfully publishing results.

Tried to make it conditional following instructions "importing existing publishers" https://wiki.jenkins-ci.org/display/JENKINS/Flexible+Publish+Plugin

```
import static org.jenkins_ci.plugins.flexible_publish.JobUpdater.*

def job = hudson.model.Hudson.instance.getItem('modulesJavaDatastore')
list job
movePublisher job,'Coverity'
list job
```

Maven build completed successfully, then follows following exception in console log.

Strings match run condition: string 1=[clean], string 2=[clean]
Run condition [Strings match] enabling perform for step [Coverity]
ERROR: Publisher org.jenkins_ci.plugins.flexible_publish.FlexiblePublisher aborted due to exception
java.lang.NullPointerException
at jenkins.plugins.coverity.CoverityPublisher.perform(CoverityPublisher.java:404)
at org.jenkins_ci.plugins.run_condition.BuildStepRunner$2.run(BuildStepRunner.java:110)
at org.jenkins_ci.plugins.run_condition.BuildStepRunner$DontRun.conditionalRun(BuildStepRunner.java:264)
at org.jenkins_ci.plugins.run_condition.BuildStepRunner.perform(BuildStepRunner.java:105)
at org.jenkins_ci.plugins.flexible_publish.ConditionalPublisher.perform(ConditionalPublisher.java:134)
at org.jenkins_ci.plugins.flexible_publish.FlexiblePublisher.perform(FlexiblePublisher.java:111)
at hudson.tasks.BuildStepMonitor$2.perform(BuildStepMonitor.java:32)
at hudson.model.AbstractBuild$AbstractBuildExecution.perform(AbstractBuild.java:782)
at hudson.model.AbstractBuild$AbstractBuildExecution.performAllBuildSteps(AbstractBuild.java:754)
at hudson.maven.MavenModuleSetBuild$MavenModuleSetBuildExecution.post2(MavenModuleSetBuild.java:1020)
at hudson.model.AbstractBuild$AbstractBuildExecution.post(AbstractBuild.java:707)
at hudson.model.Run.execute(Run.java:1690)
at hudson.maven.MavenModuleSetBuild.run(MavenModuleSetBuild.java:509)
at hudson.model.ResourceController.execute(ResourceController.java:88)
at hudson.model.Executor.run(Executor.java:246)
[WARNINGS] Skipping publisher since build result is FAILURE