Open Radar

 
Summary:
UICollectionView crashes in -performBatchUpdates: when header view is nil

Steps to Reproduce:
1) Run the attached project in the simulator

Or

1) Set a header size in UICollectionView, but don't provide a supplementary view
2) Invoke -performBatchUpdates with an empty block

Expected Results:
Leaves space for a header view without actually drawing it. This is identical to what would happen if you don't call -performBatchUpdates.

Actual Results:
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** setObjectForKey: object cannot be nil (key: <_UICollectionViewItemKey: 0x109440b0> Type = SV Kind = UICollectionElementKindSectionHeader IndexPath = <NSIndexPath 0x10944080> 2 indexes [0, 0])'

* thread #1: tid = 0x1f03, 0x010d0e52 libobjc.A.dylib`objc_exception_throw, stop reason = breakpoint 1.3
    frame #0: 0x010d0e52 libobjc.A.dylib`objc_exception_throw
    frame #1: 0x01d160de CoreFoundation`-[__NSDictionaryM setObject:forKey:] + 158
    frame #2: 0x00515aa0 UIKit`-[UICollectionView _setVisibleSupplementaryView:forKind:indexPath:] + 93
    frame #3: 0x005258f9 UIKit`-[UICollectionView _viewAnimationsForCurrentUpdate] + 6745
    frame #4: 0x005266f8 UIKit`-[UICollectionView _updateWithItems:] + 1615
    frame #5: 0x00523bdb UIKit`-[UICollectionView _endItemAnimations] + 13286
    frame #6: 0x005275f5 UIKit`-[UICollectionView _endUpdates] + 48
    frame #7: 0x005276b9 UIKit`-[UICollectionView performBatchUpdates:completion:] + 191
    frame #8: 0x00003627 UICollectionViewBug`-[ViewController setItems:](self=0x075504c0, _cmd=0x005bce1d, items=0x07551190) + 231 at ViewController.m:59
    frame #9: 0x0000322f UICollectionViewBug`-[ViewController viewDidLoad](self=0x075504c0, _cmd=0x005c7a77) + 463 at ViewController.m:34
    frame #10: 0x000f61c7 UIKit`-[UIViewController loadViewIfRequired] + 536
    frame #11: 0x000f6232 UIKit`-[UIViewController view] + 33
    frame #12: 0x000453d5 UIKit`-[UIWindow addRootViewControllerViewIfPossible] + 66
    frame #13: 0x0004576f UIKit`-[UIWindow _setHidden:forced:] + 368
    frame #14: 0x00045905 UIKit`-[UIWindow _orderFrontWithoutMakingKey] + 49
    frame #15: 0x0004e917 UIKit`-[UIWindow makeKeyAndVisible] + 65
    frame #16: 0x00002c55 UICollectionViewBug`-[AppDelegate application:didFinishLaunchingWithOptions:](self=0x0754ada0, _cmd=0x005abc21, application=0x07649cf0, launchOptions=0x00000000) + 661 at AppDelegate.m:21
    frame #17: 0x00012157 UIKit`-[UIApplication _handleDelegateCallbacksWithOptions:isSuspended:restoreState:] + 266
    frame #18: 0x00012747 UIKit`-[UIApplication _callInitializationDelegatesForURL:payload:suspended:] + 1248
    frame #19: 0x0001394b UIKit`-[UIApplication _runWithURL:payload:launchOrientation:statusBarStyle:statusBarHidden:] + 805
    frame #20: 0x00024cb5 UIKit`-[UIApplication handleEvent:withNewEvent:] + 1022
    frame #21: 0x00025beb UIKit`-[UIApplication sendEvent:] + 85
    frame #22: 0x00017698 UIKit`_UIApplicationHandleEvent + 9874
    frame #23: 0x01beedf9 GraphicsServices`_PurpleEventCallback + 339
    frame #24: 0x01beead0 GraphicsServices`PurpleEventCallback + 46
    frame #25: 0x01c08bf5 CoreFoundation`__CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 53
    frame #26: 0x01c08962 CoreFoundation`__CFRunLoopDoSource1 + 146
    frame #27: 0x01c39bb6 CoreFoundation`__CFRunLoopRun + 2118
    frame #28: 0x01c38f44 CoreFoundation`CFRunLoopRunSpecific + 276
    frame #29: 0x01c38e1b CoreFoundation`CFRunLoopRunInMode + 123
    frame #30: 0x0001317a UIKit`-[UIApplication _run] + 774
    frame #31: 0x00014ffc UIKit`UIApplicationMain + 1211
    frame #32: 0x0000298d UICollectionViewBug`main(argc=1, argv=0xbffff364) + 141 at main.m:16
    frame #33: 0x000028b5 UICollectionViewBug`start + 53

Regression:
The results occur on iOS 6.1.

Notes:
In ViewController.m, set WANT_CRASH to 0 to skip the call to -performBatchUpdates:, which prevents the crash.