[SPARK-5703] AllJobsPage throws empty.max exception

If you have a `SparkListenerJobEnd` event without the corresponding `SparkListenerJobStart` event, then `JobProgressListener` will create an empty `JobUIData` with an empty `stageIds` list. However, later in `AllJobsPage` we call `stageIds.max`. If this is empty, it will throw an exception.

This crashed my history server.

Author: Andrew Or <andrew@databricks.com>

Closes #4490 from andrewor14/jobs-page-max and squashes the following commits:

21797d3 [Andrew Or] Check nonEmpty before calling max

core/src/main/scala/org/apache/spark/ui/jobs/AllJobsPage.scala

@@ -42,7 +42,9 @@ private[ui] class AllJobsPage(parent: JobsTab) extends WebUIPage("") {
     }
 
     def makeRow(job: JobUIData): Seq[Node] = {
-      val lastStageInfo = listener.stageIdToInfo.get(job.stageIds.max)
+      val lastStageInfo = Option(job.stageIds)
+        .filter(_.nonEmpty)
+        .flatMap { ids => listener.stageIdToInfo.get(ids.max) }
       val lastStageData = lastStageInfo.flatMap { s =>
         listener.stageIdToData.get((s.stageId, s.attemptId))
       }