Removed references to `self.viewController` from the ATUtilities version of `rootViewControllerForCurrentWindow`
Removed references to `self.viewController` from the ATUtilities version of `rootViewControllerForCurrentWindow`

ALHariPrasad/apptentive-ios,hibu/apptentive-ios,apptentive/apptentive-ios,apptentive/apptentive-ios,hibu/apptentive-ios,ALHariPrasad/apptentive-ios,apptentive/apptentive-ios,Jawbone/apptentive-ios,Jawbone/apptentive-ios,hibu/apptentive-ios,sahara108/apptentive-ios,sahara108/apptentive-ios