Seen this when submodules are selected. I think this happens when the build settings change and we get a first time build.

12:51:26 First time build. Skipping changelog.
12:51:26 FATAL: null
12:51:26 java.lang.NullPointerException
12:51:26 at hudson.plugins.git.extensions.impl.SubmoduleOption.onCheckoutCompleted(SubmoduleOption.java:82)
12:51:26 at hudson.plugins.git.GitSCM.checkout(GitSCM.java:1074)
12:51:26 at hudson.scm.SCM.checkout(SCM.java:485)
12:51:26 at hudson.model.AbstractProject.checkout(AbstractProject.java:1276)
12:51:26 at hudson.model.AbstractBuild$AbstractBuildExecution.defaultCheckout(AbstractBuild.java:607)
12:51:26 at jenkins.scm.SCMCheckoutStrategy.checkout(SCMCheckoutStrategy.java:86)
12:51:26 at hudson.model.AbstractBuild$AbstractBuildExecution.run(AbstractBuild.java:529)
12:51:26 at hudson.model.Run.execute(Run.java:1738)
12:51:26 at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:43)
12:51:26 at hudson.model.ResourceController.execute(ResourceController.java:98)
12:51:26 at hudson.model.Executor.run(Executor.java:410)