Running FitNesse tests results in a build failure with the following stack-trace:

Starting new Fitnesse instance...
java.lang.NullPointerException
at hudson.Launcher.printCommandLine(Launcher.java:634)
at hudson.Launcher.maskedPrintCommandLine(Launcher.java:656)
at hudson.Launcher$LocalLauncher.launch(Launcher.java:792)
at hudson.Launcher$ProcStarter.start(Launcher.java:380)
at hudson.plugins.fitnesse.FitnesseExecutor.startFitnesse(FitnesseExecutor.java:81)
at hudson.plugins.fitnesse.FitnesseExecutor.execute(FitnesseExecutor.java:48)
at hudson.plugins.fitnesse.FitnesseBuilder.perform(FitnesseBuilder.java:270)
at hudson.tasks.BuildStepMonitor$1.perform(BuildStepMonitor.java:20)
at hudson.model.AbstractBuild$AbstractBuildExecution.perform(AbstractBuild.java:770)
at hudson.model.Build$BuildExecution.build(Build.java:199)
at hudson.model.Build$BuildExecution.doRun(Build.java:160)
at hudson.model.AbstractBuild$AbstractBuildExecution.run(AbstractBuild.java:533)
at hudson.model.Run.execute(Run.java:1745)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:43)
at hudson.model.ResourceController.execute(ResourceController.java:89)
at hudson.model.Executor.run(Executor.java:240)

Configuration is:
<hudson.plugins.fitnesse.FitnesseBuilder plugin="fitnesse@1.9">
<options>
<entry>
<string>fitnesseJavaOpts</string>
<string></string>
</entry>
<entry>
<string>fitnesseHttpTimeout</string>
<string>600000</string>
</entry>
<entry>
<string>fitnessePathToRoot</string>
<string>root</string>
</entry>
<entry>
<string>fitnesseStart</string>
<string>True</string>
</entry>
<entry>
<string>fitnesseJdk</string>
<string>Oracle JDK 7</string>
</entry>
<entry>
<string>fitnessePortLocal</string>
<string>7999</string>
</entry>
<entry>
<string>fitnesseTargetPage</string>
<string>TestSuite</string>
</entry>
<entry>
<string>fitnessePathToJar</string>
<string>fitnesse-standalone.jar</string>
</entry>
<entry>
<string>fitnesseTargetIsSuite</string>
<string>true</string>
</entry>
<entry>
<string>fitnesseTestTimeout</string>
<string>600000</string>
</entry>
<entry>
<string>additionalFitnesseOptions</string>
<string></string>
</entry>
<entry>
<string>fitnesseJavaWorkingDirectory</string>
<string></string>
</entry>
<entry>
<string>fitnessePathToXmlResultsOut</string>
<string>fitnesse.xml</string>
</entry>
</options>
</hudson.plugins.fitnesse.FitnesseBuilder>