Issue with package-quick-start (+ another issue)

[Ergus]

Hi:

Recently trying the master branch; emacs fails to start with a message:

```
Wrong type argument: stringp, nil
```

which seems to happen after window-setup-hook.

When I remove package-quickstart.el[c] then it goes back to normal and
everything works fine. I tried --debug-init but I don't get any
information, just the message... Is there a method to get more
information about what's going on??

I don't report this as a bug because it can't be reproduce it with -Q
(as -Q never loads the quick-start) and I can't be sure this is an issue
in my config, external package or emacs issue.

BTW:

There is a behavior difference here a bit annoying:

Using -nw emacs starts and shows the error in the echo area, which is
very bad because with this failure emacs is non functional and I can't
see the *messages* buffer

When NOT using -nw emacs never starts and the errors are shown inline
immediately...

Shouldn't these two behaviors be consistent and behave the same??

Best,
Ergus