Steps to Reproduce:

1. With the above installed, create a job with "Execute Docker command" which does:

Pull Image

Name: owasp/zap2docker-weekly
Tag: latest
Registry: [blank[ or Docker
Docker Registry URL; https://hub.docker.com/r/owasp/zap2docker-weekly/
Registry Credentials: [none]

2. In Jenkins, click "Build Now"

Actual Results:

I get the following stack trace/exception:

Started by user anonymous
Building in workspace /var/lib/jenkins/workspace/Docker-ZAP
> /usr/bin/git rev-parse --is-inside-work-tree # timeout=10
Fetching changes from the remote Git repository
> /usr/bin/git config remote.origin.url https://github.com/stephendonner/docker-zap.git # timeout=10
Fetching upstream changes from https://github.com/stephendonner/docker-zap.git
> /usr/bin/git --version # timeout=10
> /usr/bin/git -c core.askpass=true fetch --tags --progress https://github.com/stephendonner/docker-zap.git +refs/heads/:refs/remotes/origin/
> /usr/bin/git rev-parse refs/remotes/origin/master^

# timeout=10
Checking out Revision 827ab1e2eb5888f8b612610fe3f6b9f62f7e219f (refs/remotes/origin/master)
> /usr/bin/git config core.sparsecheckout # timeout=10
> /usr/bin/git checkout -f 827ab1e2eb5888f8b612610fe3f6b9f62f7e219f
> /usr/bin/git rev-list 827ab1e2eb5888f8b612610fe3f6b9f62f7e219f # timeout=10
ERROR: Build step failed with exception
java.lang.NullPointerException
at com.github.dockerjava.jaxrs.DockerCmdExecFactoryImpl.init(DockerCmdExecFactoryImpl.java:105)
at com.github.dockerjava.core.DockerClientImpl.withDockerCmdExecFactory(DockerClientImpl.java:64)
at com.github.dockerjava.core.DockerClientBuilder.build(DockerClientBuilder.java:63)
at org.jenkinsci.plugins.dockerbuildstep.DockerBuilder$DescriptorImpl.createDockerClient(DockerBuilder.java:132)
at org.jenkinsci.plugins.dockerbuildstep.DockerBuilder$DescriptorImpl.getDockerClient(DockerBuilder.java:204)
at org.jenkinsci.plugins.dockerbuildstep.DockerBuilder.perform(DockerBuilder.java:68)
at hudson.tasks.BuildStepMonitor$1.perform(BuildStepMonitor.java:20)
at hudson.model.AbstractBuild$AbstractBuildExecution.perform(AbstractBuild.java:782)
at hudson.model.Build$BuildExecution.build(Build.java:205)
at hudson.model.Build$BuildExecution.doRun(Build.java:162)
at hudson.model.AbstractBuild$AbstractBuildExecution.run(AbstractBuild.java:534)
at hudson.model.Run.execute(Run.java:1738)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:43)
at hudson.model.ResourceController.execute(ResourceController.java:98)
at hudson.model.Executor.run(Executor.java:410)
Build step 'Execute Docker command' marked build as failure
Finished: FAILURE