Created a new milestone. But cannot import columns from other milestone.

Steps 1:

1. create milestone
2. create workboard
3. select import column
4. search for milstone with columns
5. nothing happen (no autocomplete, no error)

Steps 2:

1. create milestone
2. create workboard
3. select import column
4. click on
5. search for milestone with columns: "alli" (ref: screenshot)
6. exception occur

phabricator b2cdebefea836011d1baa75e14b587bd8dbe869d (Sat, Nov 26) 
arcanist fad85844314b151994769a461825c90f7400c145 (Oct 22 2016) 
phutil 42d7ebd477f994820f54c08ccb8485ca6262c8b6 (Fri, Nov 25)