mongo localhost:27018                                                                                                                                  
MongoDB shell version: 2.6.10
connecting to: localhost:27018/test
SHARD04:ARBITER> db.printSlaveReplicationInfo()
source: mgsh43.avoscloud.com:27018
assert failed : how could this be null (getReplLag startOptimeDate)
Error: assert failed : how could this be null (getReplLag startOptimeDate)
    at Error (<anonymous>)
    at doassert (src/mongo/shell/assert.js:11:14)
    at assert (src/mongo/shell/assert.js:20:5)
    at getReplLag (src/mongo/shell/db.js:768:9)
    at r (src/mongo/shell/db.js:809:13)
    at Array.forEach (native)
    at DB.printSlaveReplicationInfo (src/mongo/shell/db.js:821:24)
    at (shell):1:4
2015-06-03T16:33:10.395+0800 Error: assert failed : how could this be null (getReplLag startOptimeDate) at src/mongo/shell/assert.js:13
SHARD04:ARBITER>