DependencyPath feature extractor failing

[danyaljj]

[error] Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
[error] 	at java.util.ArrayList.rangeCheck(ArrayList.java:653)
[error] 	at java.util.ArrayList.get(ArrayList.java:429)
[error] 	at edu.illinois.cs.cogcomp.edison.features.factory.DependencyPath.getFeatures(DependencyPath.java:73)
[error] 	at edu.illinois.cs.cogcomp.edison.features.factory.DependencyPath.getFeatures(DependencyPath.java:51)
[error] 	at edu.illinois.cs.cogcomp.edison.features.factory.FeatureExtractorPairConjunction.getCombinedFeaturesImplementation(FeatureExtractorPairConjunction.java:43)
[error] 	at edu.illinois.cs.cogcomp.edison.features.factory.PairExtractor.getCombinedFeatures(PairExtractor.java:79)
[error] 	at org.allenai.ari.solvers.squad.features.FeatureExtractors$$anonfun$3.apply(FeatureExtractors.scala:200)
[error] 	at org.allenai.ari.solvers.squad.features.FeatureExtractors$$anonfun$3.apply(FeatureExtractors.scala:199)
[error] 	at scala.collection.TraversableLike$$anonfun$flatMap$1.apply(TraversableLike.scala:241)
[error] 	at scala.collection.TraversableLike$$anonfun$flatMap$1.apply(TraversableLike.scala:241)
[error] 	at scala.collection.immutable.List.foreach(List.scala:381)
[error] 	at scala.collection.TraversableLike$class.flatMap(TraversableLike.scala:241)
[error] 	at scala.collection.immutable.List.flatMap(List.scala:344)
[error] 	at org.allenai.ari.solvers.squad.features.FeatureExtractors$.extractTokenFeatures(FeatureExtractors.scala:199)
[error] 	at org.allenai.ari.solvers.squad.classifier.SquadClassifier$$anonfun$singleQuestionFeatureExtractor$2.apply(SquadClassifier.scala:378)
[error] 	at org.allenai.ari.solvers.squad.classifier.SquadClassifier$$anonfun$singleQuestionFeatureExtractor$2.apply(SquadClassifier.scala:336)
[error] 	at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:234)
[error] 	at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:234)
[error] 	at scala.collection.immutable.Range.foreach(Range.scala:160)
[error] 	at scala.collection.TraversableLike$class.map(TraversableLike.scala:234)
[error] 	at scala.collection.AbstractTraversable.map(Traversable.scala:104)
[error] 	at org.allenai.ari.solvers.squad.classifier.SquadClassifier$.singleQuestionFeatureExtractor(SquadClassifier.scala:336)
[error] 	at org.allenai.ari.solvers.squad.classifier.SquadClassifier$$anonfun$paragraphTrainer$1$$anonfun$1$$anonfun$apply$1.apply$mcVI$sp(SquadClassifier.scala:116)
[error] 	at scala.collection.immutable.Range.foreach$mVc$sp(Range.scala:160)
[error] 	at org.allenai.ari.solvers.squad.classifier.SquadClassifier$$anonfun$paragraphTrainer$1$$anonfun$1.apply(SquadClassifier.scala:115)
[error] 	at org.allenai.ari.solvers.squad.classifier.SquadClassifier$$anonfun$paragraphTrainer$1$$anonfun$1.apply(SquadClassifier.scala:108)
[error] 	at scala.collection.immutable.List.foreach(List.scala:381)
[error] 	at scala.collection.generic.TraversableForwarder$class.foreach(TraversableForwarder.scala:35)
[error] 	at scala.collection.mutable.ListBuffer.foreach(ListBuffer.scala:45)
[error] 	at org.allenai.ari.solvers.squad.classifier.SquadClassifier$$anonfun$paragraphTrainer$1.apply$mcVI$sp(SquadClassifier.scala:108)
[error] 	at scala.collection.immutable.Range.foreach$mVc$sp(Range.scala:160)
[error] 	at org.allenai.ari.solvers.squad.classifier.SquadClassifier$.paragraphTrainer(SquadClassifier.scala:107)
[error] 	at org.allenai.ari.solvers.squad.ExperimentsApp$.main(ExperimentsApp.scala:42)
[error] 	at org.allenai.ari.solvers.squad.ExperimentsApp.main(ExperimentsApp.scala)