Module succeeds:
Started by upstream project "common" build number 164

Module fails
Started by upstream project "common" build number 165
Building on master
FATAL: null
java.lang.NullPointerException
at
hudson.maven.MavenBuild$RunnerImpl.decideWorkspace(MavenBuild.java:481)
at hudson.model.AbstractBuild$AbstractRunner.run(AbstractBuild.java:343)
at hudson.model.Run.run(Run.java:1090)
at hudson.maven.MavenBuild.run(MavenBuild.java:200)
at hudson.model.ResourceController.execute(ResourceController.java:93)
at hudson.model.Executor.run(Executor.java:122)

These show up as all sub-builds of the Tools aggregator

This is with Hudson 1.320, build options "Build modules in parallel", "Use
private workspace" and "Block build" are enabled

If I turn off "build modules in parallel" the build succeeds (due to whole
module building, I guess).

The 'common' project is not part of the multi-module project.