Ignore setRole if switch is not connected to that node.

Change-Id: I40fb0b768294926924b29c7715a91c95df9b9664
diff --git a/openflow/ctl/src/main/java/org/onlab/onos/openflow/controller/impl/OpenFlowControllerImpl.java b/openflow/ctl/src/main/java/org/onlab/onos/openflow/controller/impl/OpenFlowControllerImpl.java
index eb12286..e8ebcd1 100644
--- a/openflow/ctl/src/main/java/org/onlab/onos/openflow/controller/impl/OpenFlowControllerImpl.java
+++ b/openflow/ctl/src/main/java/org/onlab/onos/openflow/controller/impl/OpenFlowControllerImpl.java
@@ -169,7 +169,12 @@
 
     @Override
     public void setRole(Dpid dpid, RoleState role) {
-        getSwitch(dpid).setRole(role);
+        final OpenFlowSwitch sw = getSwitch(dpid);
+        if (sw == null) {
+            log.debug("Switch not connected. Ignoring setRole({}, {})", dpid, role);
+            return;
+        }
+        sw.setRole(role);
     }
 
     /**