You can clone with
No one assigned
This is from doing hub pull-request on a detached head.
/usr/local/bin/hub:1271:in `pull_request': undefined method `upstream' for nil:NilClass (NoMethodError)
from /usr/local/bin/hub:1214:in `send'
from /usr/local/bin/hub:1214:in `run'
from /usr/local/bin/hub:1999:in `initialize'
from /usr/local/bin/hub:2003:in `new'
from /usr/local/bin/hub:2003:in `execute'
The error message should be a little more friendly.
Fixed in 70a62f8