java.lang.IllegalArgumentException
   at org.netbeans.modules.scala.core.ScalaSourceUtil$.getMainClasses(ScalaSourceUtil.java:669)
   at org.netbeans.modules.scala.core.ScalaSourceUtil$.getMainClassesAsJavaCollection(ScalaSourceUtil.java:715)
   at org.netbeans.modules.scala.core.ScalaSourceUtil$$anonfun$getMainClassesAsJavaCollection$2.apply(ScalaSourceUtil.java:728)
   at org.netbeans.modules.scala.core.ScalaSourceUtil$$anonfun$getMainClassesAsJavaCollection$2.apply(ScalaSourceUtil.java:727)
   at scala.collection.IndexedSeqOptimized$class.foreach(IndexedSeqOptimized.java:35)
   at scala.collection.mutable.ArrayOps.foreach(ArrayOps.java:35)
   at org.netbeans.modules.scala.core.ScalaSourceUtil$.getMainClassesAsJavaCollection(ScalaSourceUtil.java:727)
   at org.netbeans.modules.scala.core.ScalaSourceUtil.getMainClassesAsJavaCollection(ScalaSourceUtil.java:0)
   at org.netbeans.modules.scala.project.ui.customizer.MainClassChooser$3.run(MainClassChooser.java:147)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:602)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:1084)