[SPOT-ML] next on empty iterator

spark exception:

 
Exception in thread "main" java.util.NoSuchElementException: next on empty iterator
at scala.collection.Iterator$$anon$2.next(Iterator.scala:39)
at scala.collection.Iterator$$anon$2.next(Iterator.scala:37)
at scala.collection.IndexedSeqLike$Elements.next(IndexedSeqLike.scala:63)
at scala.collection.IterableLike$class.head(IterableLike.scala:107)
at scala.collection.mutable.ArrayOps$ofRef.scala$collection$IndexedSeqOptimized$$super$head(ArrayOps.scala:186)
at scala.collection.IndexedSeqOptimized$class.head(IndexedSeqOptimized.scala:126)
at scala.collection.mutable.ArrayOps$ofRef.head(ArrayOps.scala:186)
at org.apache.spark.mllib.clustering.EMLDAOptimizer.initialize(LDAOptimizer.scala:166)
at org.apache.spark.mllib.clustering.EMLDAOptimizer.initialize(LDAOptimizer.scala:80)
at org.apache.spark.mllib.clustering.LDA.run(LDA.scala:331)
at org.apache.spot.lda.SpotLDAWrapper$.run(SpotLDAWrapper.scala:93)
at org.apache.spot.dns.model.DNSSuspiciousConnectsModel$.trainModel(DNSSuspiciousConnectsModel.scala:175)
at org.apache.spot.dns.DNSSuspiciousConnectsAnalysis$.run(DNSSuspiciousConnectsAnalysis.scala:86)
at org.apache.spot.SuspiciousConnects$.main(SuspiciousConnects.scala:76)
at org.apache.spot.SuspiciousConnects.main(SuspiciousConnects.scala)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.apache.spark.deploy.SparkSubmit$.org$apache$spark$deploy$SparkSubmit$$runMain(SparkSubmit.scala:755)
at org.apache.spark.deploy.SparkSubmit$.doRunMain$1(SparkSubmit.scala:180)
at org.apache.spark.deploy.SparkSubmit$.submit(SparkSubmit.scala:205)
at org.apache.spark.deploy.SparkSubmit$.main(SparkSubmit.scala:119)
at org.apache.spark.deploy.SparkSubmit.main(SparkSubmit.scala)