spark萌新求问java.lang.NullPointerException

就是，我在调用了graphX的pregel接口，做了一个sparql查询系统，然后当数据比较小的时候没有什么问题，但是当数据比较大的时候，就会出现一下问题：
Caused by: java.lang.NullPointerException
at SparqlSpark.Main$.SparqlSpark$Main$$vertexProgram$1(main.scala:234)
at SparqlSpark.Main$$anonfun$14.apply(main.scala:241)
at SparqlSpark.Main$$anonfun$14.apply(main.scala:241)
at org.apache.spark.graphx.Pregel$$anonfun$1.apply(Pregel.scala:122)
at org.apache.spark.graphx.Pregel$$anonfun$1.apply(Pregel.scala:122)
at org.apache.spark.graphx.impl.VertexPartitionBaseOps.map(VertexPartitionBaseOps.scala:62)
at org.apache.spark.graphx.impl.GraphImpl$$anonfun$5.apply(GraphImpl.scala:132)
at org.apache.spark.graphx.impl.GraphImpl$$anonfun$5.apply(GraphImpl.scala:132)
at scala.collection.Iterator$$anon$11.next(Iterator.scala:328)
at org.apache.spark.storage.MemoryStore.unrollSafely(MemoryStore.scala:285)
at org.apache.spark.CacheManager.putInBlockManager(CacheManager.scala:171)
at org.apache.spark.CacheManager.getOrCompute(CacheManager.scala:78)
at org.apache.spark.rdd.RDD.iterator(RDD.scala:268)
at org.apache.spark.rdd.ZippedPartitionsRDD2.compute(ZippedPartitionsRDD.scala:88)
at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:306)
at org.apache.spark.rdd.RDD.iterator(RDD.scala:270)
at org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:38)
at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:306)
at org.apache.spark.rdd.RDD.iterator(RDD.scala:270)
at org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:73)
at org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:41)
at org.apache.spark.scheduler.Task.run(Task.scala:89)
at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:214)
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)
我调试的时候发现当数据变大的时候，图中顶点的属性有的为空。
问一下各位有没有遇到类似的情况，神马情况下会出现这种错误。分布式情况下遇到java.lang.NullPointerException该怎么解决。
谢谢各位了。