Stacktrace for issue nd4j#861

nd4j#861

java.lang.IllegalStateException: Unable to get number of of columns for a non 2d matrix
	at org.nd4j.linalg.api.ndarray.BaseNDArray.columns(BaseNDArray.java:3443)
	at org.nd4j.linalg.dataset.DataSet.merge(DataSet.java:117)
	at org.deeplearning4j.spark.impl.multilayer.IterativeReduceFlatMap.call(IterativeReduceFlatMap.java:85)
	at org.deeplearning4j.spark.impl.multilayer.IterativeReduceFlatMap.call(IterativeReduceFlatMap.java:49)
	at org.apache.spark.api.java.JavaRDDLike$$anonfun$fn$5$1.apply(JavaRDDLike.scala:160)
	at org.apache.spark.api.java.JavaRDDLike$$anonfun$fn$5$1.apply(JavaRDDLike.scala:160)
	at org.apache.spark.rdd.RDD$$anonfun$14.apply(RDD.scala:634)
	at org.apache.spark.rdd.RDD$$anonfun$14.apply(RDD.scala:634)
	at org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:35)
	at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:277)
	at org.apache.spark.CacheManager.getOrCompute(CacheManager.scala:70)
	at org.apache.spark.rdd.RDD.iterator(RDD.scala:242)
	at org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:35)
	at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:277)
	at org.apache.spark.rdd.RDD.iterator(RDD.scala:244)
	at org.apache.spark.scheduler.ResultTask.runTask(ResultTask.scala:61)
	at org.apache.spark.scheduler.Task.run(Task.scala:64)
	at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:203)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at java.lang.Thread.run(Thread.java:745)