db.printSlaveReplicationInfo()/rs.printSlaveReplicationInfo() can not work with ARBITER role

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>