Encountered error in module:                     
UpdateNumberOfLightsToStackWorker

Error message: 
java.lang.NullPointerException

Cause: 
null
if.a(Unknown Source)
if.doInBackground(Unknown Source)
javax.swing.SwingWorker$1.call(SwingWorker.java:295)
java.util.concurrent.FutureTask.run(FutureTask.java:266)