title: Running GBM on H2O Flow produces job failure: java.lang.NullPointerException
body: <p>running an H2O Flow I've already successfully run in the past on a Mac OS with the following configuration:</p>
  
  <pre><code>04-18 22:50:02.722 192.168.0.11:54321    684    main      INFO: ----- H2O started  -----
  04-18 22:50:02.723 192.168.0.11:54321    684    main      INFO: Build git branch: rel-wolpert
  04-18 22:50:02.723 192.168.0.11:54321    684    main      INFO: Build git hash: 6903ba4b4cfcd912f15cf61965f88bb13bbc4890
  04-18 22:50:02.723 192.168.0.11:54321    684    main      INFO: Build git describe: jenkins-3.18.0.3-6-g6903ba4
  04-18 22:50:02.723 192.168.0.11:54321    684    main      INFO: Build project version: 3.18.0.4 (latest version: 3.18.0.7)
  04-18 22:50:02.723 192.168.0.11:54321    684    main      INFO: Build age: 1 month and 10 days
  04-18 22:50:02.723 192.168.0.11:54321    684    main      INFO: Built by: 'jenkins'
  04-18 22:50:02.723 192.168.0.11:54321    684    main      INFO: Built on: '2018-03-08 19:15:57'
  04-18 22:50:02.723 192.168.0.11:54321    684    main      INFO: Watchdog Build git branch: (unknown)
  04-18 22:50:02.724 192.168.0.11:54321    684    main      INFO: Watchdog Build git hash: (unknown)
  04-18 22:50:02.724 192.168.0.11:54321    684    main      INFO: Watchdog Build git describe: (unknown)
  04-18 22:50:02.724 192.168.0.11:54321    684    main      INFO: Watchdog Build project version: (unknown)
  04-18 22:50:02.724 192.168.0.11:54321    684    main      INFO: Watchdog Built by: (unknown)
  04-18 22:50:02.724 192.168.0.11:54321    684    main      INFO: Watchdog Built on: (unknown)
  04-18 22:50:02.724 192.168.0.11:54321    684    main      INFO: XGBoost Build git branch: (unknown)
  04-18 22:50:02.724 192.168.0.11:54321    684    main      INFO: XGBoost Build git hash: (unknown)
  04-18 22:50:02.725 192.168.0.11:54321    684    main      INFO: XGBoost Build git describe: (unknown)
  04-18 22:50:02.725 192.168.0.11:54321    684    main      INFO: XGBoost Build project version: (unknown)
  04-18 22:50:02.725 192.168.0.11:54321    684    main      INFO: XGBoost Built by: (unknown)
  04-18 22:50:02.725 192.168.0.11:54321    684    main      INFO: XGBoost Built on: (unknown)
  04-18 22:50:02.725 192.168.0.11:54321    684    main      INFO: KrbStandalone Build git branch: (unknown)
  04-18 22:50:02.725 192.168.0.11:54321    684    main      INFO: KrbStandalone Build git hash: (unknown)
  04-18 22:50:02.725 192.168.0.11:54321    684    main      INFO: KrbStandalone Build git describe: (unknown)
  04-18 22:50:02.726 192.168.0.11:54321    684    main      INFO: KrbStandalone Build project version: (unknown)
  04-18 22:50:02.726 192.168.0.11:54321    684    main      INFO: KrbStandalone Built by: (unknown)
  04-18 22:50:02.726 192.168.0.11:54321    684    main      INFO: KrbStandalone Built on: (unknown)
  04-18 22:50:02.726 192.168.0.11:54321    684    main      INFO: Processed H2O arguments: []
  04-18 22:50:02.726 192.168.0.11:54321    684    main      INFO: Java availableProcessors: 4
  04-18 22:50:02.726 192.168.0.11:54321    684    main      INFO: Java heap totalMemory: 245.5 MB
  04-18 22:50:02.726 192.168.0.11:54321    684    main      INFO: Java heap maxMemory: 10.67 GB
  04-18 22:50:02.726 192.168.0.11:54321    684    main      INFO: Java version: Java 1.8.0_162 (from Oracle Corporation)
  04-18 22:50:02.726 192.168.0.11:54321    684    main      INFO: JVM launch parameters: [-Xmx12g]
  04-18 22:50:02.726 192.168.0.11:54321    684    main      INFO: OS version: Mac OS X 10.12.6 (x86_64)
  04-18 22:50:02.726 192.168.0.11:54321    684    main      INFO: Machine physical memory: 16.00 GB
  04-18 22:50:02.727 192.168.0.11:54321    684    main      INFO: X-h2o-cluster-id: 1524102601065
  </code></pre>
  
  <p>My dataset has around 600k observations and ~60 features.
  When building a simple GBM model with CV5 the job stops with the following trace:</p>
  
  <pre><code>java.lang.NullPointerException
      at hex.Model$Parameters.read_unlock_frames(Model.java:331)
      at hex.ModelBuilder$Driver.compute2(ModelBuilder.java:209)
      at water.H2O$H2OCountedCompleter.compute(H2O.java:1263)
      at jsr166y.CountedCompleter.exec(CountedCompleter.java:468)
      at jsr166y.ForkJoinTask.doExec(ForkJoinTask.java:263)
      at jsr166y.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:974)
      at jsr166y.ForkJoinPool.runWorker(ForkJoinPool.java:1477)
      at jsr166y.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:104)
  </code></pre>
  
  <p>it always stops at 84% progress.</p>
  
  <p>any clue why and what to do?</p>
  
  <p>thanks
  Carmelo</p>