Added commands to list paths.
Added protection against bad input on some command-lines.
diff --git a/cli/src/main/java/org/onlab/onos/cli/net/ClusterLinksCommand.java b/cli/src/main/java/org/onlab/onos/cli/net/ClusterLinksCommand.java
index 246c39e..be5105c 100644
--- a/cli/src/main/java/org/onlab/onos/cli/net/ClusterLinksCommand.java
+++ b/cli/src/main/java/org/onlab/onos/cli/net/ClusterLinksCommand.java
@@ -24,8 +24,12 @@
         int cid = Integer.parseInt(id);
         init();
         TopologyCluster cluster = service.getCluster(topology, clusterId(cid));
-        for (Link link : service.getClusterLinks(topology, cluster)) {
-            print(linkString(link));
+        if (cluster == null) {
+            error("No such cluster %s", cid);
+        } else {
+            for (Link link : service.getClusterLinks(topology, cluster)) {
+                print(linkString(link));
+            }
         }
         return null;
     }