[ONOS-4772] Avoid throwing NPE on optical resource queries.

Change-Id: I71ac76b7b456b19a8dabf78a0ef52366867cd230

@@ -66,6 +66,10 @@ public class DefaultTributarySlotQuery extends AbstractHandlerBehaviour implemen
         DeviceService deviceService = opticalView(this.handler().get(DeviceService.class));
         Port p = deviceService.getPort(this.data().deviceId(), port);
 
+        if (p == null) {
+            return Collections.emptySet();
+        }
+
         switch (p.type()) {
             case OCH:
                 return queryOchTributarySlots(p);

@@ -52,7 +52,7 @@ public class OFOpticalSwitch13LambdaQuery extends AbstractHandlerBehaviour imple
         Port p = deviceService.getPort(this.data().deviceId(), port);
 
         // Only OMS ports expose lambda resources
-        if (!p.type().equals(Port.Type.OMS)) {
+        if (p == null || !p.type().equals(Port.Type.OMS)) {
             return Collections.emptySet();
         }