"next on empty iterator"

[hanswesterbeek]

In the words of @kiivihal:

that could very well by a mapping or harvesting issue. It happens when you run a process on something that has no content

Reproduction:

1. Upload a sipzip
2. Process, analyze and save it. This works
3. Enter OAI-PMH url
4. Press 'Harvest'. The dataset then appears as 'sourced'.
5. Press 'Process'. This appears to work but is so fast that I suspect nothing is actually done.
6. Press 'analyze'. This fails with the following stacktrace:

[error] d.DatasetActor - next on empty iterator
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.MapLike$$anon$2.next(MapLike.scala:216)
    at scala.collection.IterableLike$class.head(IterableLike.scala:107)
    at scala.collection.AbstractIterable.head(Iterable.scala:54)
    at analysis.TreeNode$.apply(TreeNode.scala:90)
    at analysis.Analyzer$$anonfun$receive$1$$anonfun$applyOrElse$1$$anonfun$apply$mcV$sp$1.apply$mcV$sp(Analyzer.scala:82)
    at analysis.Analyzer$$anonfun$receive$1$$anonfun$applyOrElse$1$$anonfun$apply$mcV$sp$1.apply(Analyzer.scala:76)
    at analysis.Analyzer$$anonfun$receive$1$$anonfun$applyOrElse$1$$anonfun$apply$mcV$sp$1.apply(Analyzer.scala:76)
    at scala.concurrent.impl.Future$PromiseCompletingRunnable.liftedTree1$1(Future.scala:24)

[hanswesterbeek]

This happens when the file NarthexFiles/devorg/datasets/enb-40-beeldmateriaal/processed/00000.xml is empty. Said file is the result of the 'process' step.

[hanswesterbeek]

Discuss this with Sjoerd to come up with a correct solution, not just fight symptoms.