Nav stack forms crash

[pachun]

If you try to push a form with more than 1 section onto a navigation stack, it crashes the app. You can set the root of the navigation controller to a form with more than one section and it works. Also, pushing a form with only a single section works with a warning upon hitting the back arrow in the nav bar. The warning says something about unobserved notifications.

[clayallsopp]

Interesting; can you upload a reproducible project?

[Omnipresent]

I believe #162 is related to this issue. In that issue I've uploaded a gist with formotion controller.

[Omnipresent]

@clayallsopp I've created a reproducible project here: https://github.com/Omnipresent/issue162