Fixed build error

eraser.spark/src/main/java/de/tudresden/inf/st/eraser/spark/Application.java

@@ -241,7 +241,6 @@ public class Application {
     return SimpleItem.of(item.getID(),
         item.getLabel(),
         item.getTopic() != null ? item.getTopic().getTopicString() : null,
-        item.isFrozen(),
         item.isSendState(),
         wrapMetaData(item.getMetaDataList()));
   }

eraser.spark/src/main/java/de/tudresden/inf/st/eraser/spark/SimpleItem.java

@@ -15,7 +15,6 @@ public class SimpleItem {
   public final String ID;
   public final String label;
   public final String topic;
-  public final boolean frozen;
   public final boolean sendState;
   public final Map<String, String> metaData;
 }