ChurnGenerator without model silently fails

src/de/tud/kom/p2psim/impl/churn/DefaultChurnGenerator.java

@@ -86,6 +86,10 @@ public class DefaultChurnGenerator implements EventHandler, ChurnGenerator {
 
 	@Override
 	public void eventOccurred(Object content, int type) {
+		if (this.churnModel == null) {
+			// fail silently if no churn model is configured.
+			return;
+		}
 		if (type == CHURN_EVENT) {
 			ChurnEvent churnEvent = (ChurnEvent) content;
 			SimNetworkComponent net = churnEvent.host.getNetworkComponent();