I am using the Cloudbees Custom tools plugin, and since version 1.525 I get the following stack :

FATAL: null
java.lang.NullPointerException
at hudson.Launcher$ProcStarter.envs(Launcher.java:302)
at com.cloudbees.jenkins.plugins.customtools.CustomToolInstallWrapper$2.launch(CustomToolInstallWrapper.java:186)
at hudson.Launcher$ProcStarter.start(Launcher.java:353)
at com.netceler.ivpower.integrationtest.utils.CommandLauncher.launchCommand(CommandLauncher.java:25)
at com.netceler.ivpower.integrationtest.install.InstallerLauncher.launchInstaller(InstallerLauncher.java:44)
at com.netceler.ivpower.integrationtest.install.InstallBuildWrapper.setUp(InstallBuildWrapper.java:106)
at hudson.model.Build$BuildExecution.doRun(Build.java:154)
at hudson.model.AbstractBuild$AbstractBuildExecution.run(AbstractBuild.java:586)
at hudson.model.Run.execute(Run.java:1593)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:46)
at hudson.model.ResourceController.execute(ResourceController.java:88)
at hudson.model.Executor.run(Executor.java:247)

I temporarly fixed the problem by adding a catch on NullPointerException on the Cloudbees plugin, but I think that the core itself should handle this case.