yes this can happen, if there no windows open.  This `openDialog` function is just sugar for the one defined in `browser.js` which I think uses similar code to the `open` method in `window/utils`.  I've made [bug 843799](https://bugzilla.mozilla.org/show_bug.cgi?id=843799) already about using `require('sdk/window/utils').open` instead of `require('sdk/window/utils').openDialog` in the `sdk/windows` module already, which is the only place that it seems to be used.  It's a tricky thing to fix tho and I don't want to mess with that here.