mitchellh/vagrant — pull request #3020 by lheinlen-os (2014-02-25 13:58:37+00:00)
Title: Do not to_s the machine id if it is nil

When destroying a machine, the machine id is set to nil. The to_s then causes it to be set to empty string. This can cause inconsistent behavior in anything (such as a plugin) that tests the machine id.