bug fix for topology change detection
diff --git a/src/main/java/net/onrc/onos/ofcontroller/flowmanager/FlowEventHandler.java b/src/main/java/net/onrc/onos/ofcontroller/flowmanager/FlowEventHandler.java
index 23b2f28..e56f0df 100644
--- a/src/main/java/net/onrc/onos/ofcontroller/flowmanager/FlowEventHandler.java
+++ b/src/main/java/net/onrc/onos/ofcontroller/flowmanager/FlowEventHandler.java
@@ -244,10 +244,10 @@
 	    TopologyElement topologyElement = eventEntry.eventData();
 	    switch (eventEntry.eventType()) {
 	    case ENTRY_ADD:
-		isTopologyModified = topology.addTopologyElement(topologyElement);
+		isTopologyModified |= topology.addTopologyElement(topologyElement);
 		break;
 	    case ENTRY_REMOVE:
-		isTopologyModified = topology.removeTopologyElement(topologyElement);
+		isTopologyModified |= topology.removeTopologyElement(topologyElement);
 		break;
 	    }
 	}