`docker -d -b=none` panics with a nil pointer

[vbatts]

http://pastebin.com/6PJb8LZ6
This was discovered while packaging: Docker version 0.7, build 457375e/0.14.rc5.el6
after checking with shykes in #docker-dev, he confirmed that he could reproduce this in 0.6.6 as well.

[vbatts]

linked bug: https://bugzilla.redhat.com/show_bug.cgi?id=1032094