typeError on changing virtualbox url

[haf]

Why do I bother trying to change things?

TypeError: Cannot read property 'browser' of null
    at /Applications/Vessel.app/Contents/Resources/app/ui/window.js:28:32
    at Function.wrappedCallback (/Applications/Vessel.app/Contents/Resources/atom/browser/api/lib/dialog.js:58:16)

Repro: initialise like your 'Getting Started'

Fiddle with the vagrantbox uri to make it 'coreos-stable'. Build environment. Fiddle with it again, switch tabs a couple of times. Go back to the view of the vagrantbox uri - now it's named 'null URL'.

You can't start or edit the URL anymore. GO TO SQUARE 1.