Get to the password screen with not enough funds

I got this error from a windows user:

![image](https://user-images.githubusercontent.com/33178835/48902384-b241f580-ee58-11e8-9f24-415ba1b079ed.png)

I could not reproduce it, but I'd consider this as a bug since the user should not land on the transaction overview/password if he doesn't have enough funds.

Could be related to https://github.com/paritytech/fether/issues/250