iOS 7 compatibility: is weak-linking UIKit required?

[cbowns]

I'm unable to get my app to launch on the iOS 7.1 Simulator:

dyld: Symbol not found: _OBJC_CLASS_$_UIAlertAction
  Referenced from: /Users/cbowns/Library/Developer/CoreSimulator/Devices/2C081425-10FD-4DC6-965F-3B43868EBEA2/data/Applications/0A94D6FB-64B8-4A0F-B0D8-0D08C51E6CFC/App.app/App

I was able to fix this by weak-linking all of UIKit, but I'm surprised that's the solution (and disappointed: weak-linking the whole framework has performance implications on the device). I would have expected advice similar to Marco's from 2011 to be applicable here: the check here seems sufficient, but it's somehow not working?

I'm wondering if the unconditional inclusion of code with UIAlertAction in UIAlertController-Blocks here is to blame.

It seems like what I'm doing should Just Work, but it's not.