zkCli throwing nullpointerException instead it should provide help when invalid input is entered

1. a) Connect to zookeeper using zkCli
b) just input space and then hit enter

2. a) Connect to zookeeper using zkCli and hit enter it will come as connected
b) just input space and then hit enter

Console log is as below:-
[zk: localhost:2181(CONNECTING) 0] 2016-08-25 16:54:48,143 [myid:] - INFO [main-SendThread(localhost:2181):ClientCnxnSocketNetty$ZKClientPipelineFactory@363] - SSL handler added for channel: null
2016-08-25 16:54:48,175 [myid:] - INFO [main-SendThread(localhost:2181):ClientCnxn$SendThread@980] - Socket connection established, initiating session, client: /0:0:0:0:0:0:0:1:44592, server: localhost/0:0:0:0:0:0:0:1:2181
2016-08-25 16:54:48,178 [myid:] - INFO [main-SendThread(localhost:2181):ClientCnxnSocketNetty$1@146] - channel is connected: [id: 0xd03f4226, /0:0:0:0:0:0:0:1:44592 => localhost/0:0:0:0:0:0:0:1:2181]
2016-08-25 16:54:48,288 [myid:] - INFO [New I/O worker #1:ClientCnxn$SendThread@1400] - Session establishment complete on server localhost/0:0:0:0:0:0:0:1:2181, sessionid = 0x101a00305cc0005, negotiated timeout = 30000

WATCHER::

WatchedEvent state:SyncConnected type:None path:null

Exception in thread "main" java.lang.NullPointerException
at org.apache.zookeeper.ZooKeeperMain$MyCommandOptions.getArgArray(ZooKeeperMain.java:171)
at org.apache.zookeeper.ZooKeeperMain.processZKCmd(ZooKeeperMain.java:613)
at org.apache.zookeeper.ZooKeeperMain.processCmd(ZooKeeperMain.java:577)
at org.apache.zookeeper.ZooKeeperMain.executeLine(ZooKeeperMain.java:360)
at org.apache.zookeeper.ZooKeeperMain.run(ZooKeeperMain.java:320)
at org.apache.zookeeper.ZooKeeperMain.main(ZooKeeperMain.java:280)

----------------------------------------
After connection is established, input space and hit enter

[zk: localhost:2181(CONNECTING) 0] 2016-08-25 16:56:22,445 [myid:] - INFO [main-SendThread(localhost:2181):ClientCnxnSocketNetty$ZKClientPipelineFactory@363] - SSL handler added for channel: null
2016-08-25 16:56:22,481 [myid:] - INFO [main-SendThread(localhost:2181):ClientCnxn$SendThread@980] - Socket connection established, initiating session, client: /0:0:0:0:0:0:0:1:44594, server: localhost/0:0:0:0:0:0:0:1:2181
2016-08-25 16:56:22,484 [myid:] - INFO [main-SendThread(localhost:2181):ClientCnxnSocketNetty$1@146] - channel is connected: [id: 0xe6d3a461, /0:0:0:0:0:0:0:1:44594 => localhost/0:0:0:0:0:0:0:1:2181]
2016-08-25 16:56:22,597 [myid:] - INFO [New I/O worker #1:ClientCnxn$SendThread@1400] - Session establishment complete on server localhost/0:0:0:0:0:0:0:1:2181, sessionid = 0x101a00305cc0007, negotiated timeout = 30000

WATCHER::

WatchedEvent state:SyncConnected type:None path:null

[zk: localhost:2181(CONNECTED) 0]
Exception in thread "main" java.lang.NullPointerException
at org.apache.zookeeper.ZooKeeperMain$MyCommandOptions.getArgArray(ZooKeeperMain.java:171)
at org.apache.zookeeper.ZooKeeperMain.processZKCmd(ZooKeeperMain.java:613)
at org.apache.zookeeper.ZooKeeperMain.processCmd(ZooKeeperMain.java:577)
at org.apache.zookeeper.ZooKeeperMain.executeLine(ZooKeeperMain.java:360)
at org.apache.zookeeper.ZooKeeperMain.run(ZooKeeperMain.java:320)
at org.apache.zookeeper.ZooKeeperMain.main(ZooKeeperMain.java:280)