NPE when executing Modularity

[Mathieu Bastian]

Reported via Crash Reporter. Looking for steps to reproduce

The graph is readLock(), so it can't be a graph consistency issue.

Stack Trace:
java.lang.NullPointerException
 at org.gephi.statistics.plugin.Modularity$CommunityStructure.<init>(Modularity.java:133)
 at org.gephi.statistics.plugin.Modularity.execute(Modularity.java:379)
 at org.gephi.statistics.plugin.Modularity.execute(Modularity.java:369)
 at org.gephi.statistics.StatisticsControllerImpl$2.run(StatisticsControllerImpl.java:118)
 at org.gephi.utils.longtask.api.LongTaskExecutor$RunningLongTask.run(LongTaskExecutor.java:228)
 at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
 at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
 at java.util.concurrent.FutureTask.run(FutureTask.java:138)
 at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)