title: UIActivityViewController crashing, NSCFConstantString _beforeActivity unrecognized selector sent to instance
body: <p>I'm trying to add the new iOS 6 sharing functionality to my app using the UIActivityViewController.  I've got some text that I want to share and if they choose Email I want to automatically set the Subject of the email as well. </p>
  
  <pre><code>NSArray *activityItems = @[resultString];
  NSLog(@"items=%@", activityItems);
  
  NSArray *acitivities = @[UIActivityTypeMail, UIActivityTypeMessage, UIActivityTypePrint, UIActivityTypePostToFacebook, UIActivityTypeCopyToPasteboard];
  
  UIActivityViewController *activityController =
      [[UIActivityViewController alloc] initWithActivityItems:activityItems
                                        applicationActivities:activities];
  
  if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) {
      self.popover = [[UIPopoverController alloc] initWithContentViewController:activityController];
      // the line above is where the error happens.
      [self.popover presentPopoverFromBarButtonItem:self.emailResultsButton permittedArrowDirections:UIPopoverArrowDirectionAny animated:YES];
  } else {
      [self presentViewController:activityController
                         animated:YES
                       completion:nil];
  }
  </code></pre>
  
  <p>Here is the output of the code including the error message:</p>
  
  <pre><code>[694:907] items=(
      "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Maecenas porttitor accumsan mi eu mollis. Fusce condimentum dictum lectus, eu ultrices urna vulputate eu."
  )
  [694:907] -[__NSCFConstantString _beforeActivity]: unrecognized selector sent to instance 0x3ad971c8
  [694:907] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFConstantString _beforeActivity]: unrecognized selector sent to instance 0x3ad971c8'
  *** First throw call stack:
  (0x35add2a3 0x37a1497f 0x35ae0e07 0x35adf531 0x35a36f68 0x361dc7a3 0x361dc52d 0x36067595 0x36434d31 0x3642fe07 0x2990b 0x361330ad 0x36133135 0x361330ad 0x3613305f 0x3613303d 0x361328f3 0x36132de9 0x3605b5f9 0x36048809 0x36048123 0x37bd15a3 0x37bd11d3 0x35ab2173 0x35ab2117 0x35ab0f99 0x35a23ebd 0x35a23d49 0x37bd02eb 0x3609c301 0x1ef9d 0x1ef30)
  libc++abi.dylib: terminate called throwing an exception
  </code></pre>
  
  <p>I'm running this on an iPad 2 with iOS6. Any ideas?</p>
  
  <p>EDIT: It appears if I do not supply the activities array then everything seems to work fine. Still narrowing down the problem.</p>