Fix #1459, Fix stop cmdlet error (#1460)

Author: littlezhou

smart-engine/src/main/java/org/smartdata/server/engine/cmdlet/agent/AgentMaster.java

@@ -278,8 +278,12 @@ private boolean handleClientMessage(Object message) {
         return true;
       } else if (message instanceof StopCmdlet) {
         long cmdletId = ((StopCmdlet) message).getCmdletId();
-        dispatches.get(cmdletId).tell(message, getSelf());
-        getSender().tell("Succeed", getSelf());
+        if (dispatches.containsKey(cmdletId)) {
+          dispatches.get(cmdletId).tell(message, getSelf());
+          getSender().tell("Succeed", getSelf());
+        } else {
+          getSender().tell("NotFound", getSelf());
+        }
         return true;
       } else {
         return false;