title: "java.lang.RuntimeException: null" while querying with Reactive Mongo 0.11
body: <p>I'm trying to query a collection with findAll with <code>selector = {}</code> on JsonCollection with Play 2.4.2 and Reactive Mongo 0.11.5.</p>
  
  <p>Query fails in method <code>foldM</code> deep inside the <code>play.api.libs.iteratee</code> while calling method <code>collect[List]</code>.</p>
  
  <p>Last code that I could trace was <code>case Input.El(e) =&gt; { val newS = executeFuture(f(s, e))(pec); flatten(newS.map(s1 =&gt; Cont[E, A](step(s1)))(dec)) }</code>.</p>
  
  <p>This code was ported from reactive mongo 0.10.5 and play 2.3.9.</p>
  
  <p>The stack trace:</p>
  
  <pre><code>java.lang.RuntimeException: null
          at scala.sys.package$.error(package.scala:27) ~[scala-library-2.11.6.jar:na]
          at play.api.libs.iteratee.Iteratee$$anonfun$run$1.apply(Iteratee.scala:396) ~[play-iteratees_2.11-2.4.2.jar:2.4.2]
          at play.api.libs.iteratee.Iteratee$$anonfun$run$1.apply(Iteratee.scala:389) ~[play-iteratees_2.11-2.4.2.jar:2.4.2]
          at play.api.libs.iteratee.StepIteratee$$anonfun$fold$2.apply(Iteratee.scala:706) ~[play-iteratees_2.11-2.4.2.jar:2.4.2]
          at play.api.libs.iteratee.StepIteratee$$anonfun$fold$2.apply(Iteratee.scala:706) ~[play-iteratees_2.11-2.4.2.jar:2.4.2]
          at scala.concurrent.impl.Future$PromiseCompletingRunnable.liftedTree1$1(Future.scala:24) ~[scala-library-2.11.6.jar:na]
          at scala.concurrent.impl.Future$PromiseCompletingRunnable.run(Future.scala:24) ~[scala-library-2.11.6.jar:na]
          at play.api.libs.iteratee.Execution$trampoline$.executeScheduled(Execution.scala:109) ~[play-iteratees_2.11-2.4.2.jar:2.4.2]
          at play.api.libs.iteratee.Execution$trampoline$.execute(Execution.scala:71) ~[play-iteratees_2.11-2.4.2.jar:2.4.2]
          at scala.concurrent.impl.CallbackRunnable.executeWithValue(Promise.scala:40) ~[scala-library-2.11.6.jar:na]
          at scala.concurrent.impl.Promise$DefaultPromise.tryComplete(Promise.scala:248) ~[scala-library-2.11.6.jar:na]
          at scala.concurrent.Promise$class.complete(Promise.scala:55) ~[scala-library-2.11.6.jar:na]
          at scala.concurrent.impl.Promise$DefaultPromise.complete(Promise.scala:153) ~[scala-library-2.11.6.jar:na]
          at scala.concurrent.impl.Future$PromiseCompletingRunnable.run(Future.scala:23) ~[scala-library-2.11.6.jar:na]
          at scala.concurrent.impl.ExecutionContextImpl$AdaptedForkJoinTask.exec(ExecutionContextImpl.scala:121) ~[scala-library-2.11.6.jar:na]
          at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260) [scala-library-2.11.6.jar:na]
          at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339) [scala-library-2.11.6.jar:na]
          at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979) [scala-library-2.11.6.jar:na]
          at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107) [scala-library-2.11.6.jar:na]
  </code></pre>