Open Radar

 
When tableView:estimatedHeightForHeaderInSection: is used when one of the table's sections have zero rows, and a cell animation (insertion, in my case) is performed in another section, the application will crash with an NSInvalidArgumentException within -[NSMutableArray insertObject:atIndex:] due to a nil value.

While troubleshooting the issue, I determined that the array of objects in question are the UITableViewCell instances that are going to participate in the animation in the -[UIView animateWithDuration:delay:options:animations:completion:] animation block.  While single-stepping the issue, the -[UITableView _updateWithItems:updateSupport:] method will interrogate the UITableViewDataSource for the cells during the update, but it only requests a few cells...certainly not enough to occupy the visible area of the screen.

Therefore, during the animation block, it doesn't request a cell from the data source, and it attempts to insert a nil value into the array.

If you either a) ensure that all sections have a minimum of 1 cell, or b) you don't use estimated section header heights, the crash will not occur.  I have attached a sample project that demonstrates the problem, with a set of instructions to demonstrate its use within the comments of ViewController.m in the zip file.

2015-12-29 17:57:07.391 TableViewCrash[42210:13929897] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[__NSArrayM insertObject:atIndex:]: object cannot be nil'
*** First throw call stack:
(
	0   CoreFoundation                      0x0000000105f19e65 __exceptionPreprocess + 165
	1   libobjc.A.dylib                     0x0000000105990deb objc_exception_throw + 48
	2   CoreFoundation                      0x0000000105de08c5 -[__NSArrayM insertObject:atIndex:] + 901
	3   UIKit                               0x00000001063fb0ac __46-[UITableView _updateWithItems:updateSupport:]_block_invoke1027 + 180
	4   UIKit                               0x0000000106374370 +[UIView(UIViewAnimationWithBlocks) _setupAnimationWithDuration:delay:view:options:factory:animations:start:animationStateGenerator:completion:] + 582
	5   UIKit                               0x00000001063747a5 +[UIView(UIViewAnimationWithBlocks) animateWithDuration:delay:options:animations:completion:] + 105
	6   UIKit                               0x00000001063facbb -[UITableView _updateWithItems:updateSupport:] + 4486
	7   UIKit                               0x00000001063f328a -[UITableView _endCellAnimationsWithContext:] + 15360
	8   TableViewCrash                      0x000000010548e466 -[ViewController setShowMoreCells:] + 486
	9   TableViewCrash                      0x000000010548de52 -[ViewController showMoreChanged:] + 482
	10  UIKit                               0x00000001062c9194 -[UIApplication sendAction:to:from:forEvent:] + 92
	11  UIKit                               0x00000001064386fc -[UIControl sendAction:to:forEvent:] + 67
	12  UIKit                               0x00000001064389c8 -[UIControl _sendActionsForEvents:withEvent:] + 311
	13  UIKit                               0x000000010665c0f6 -[_UISwitchInternalViewNeueStyle1 _setPressed:on:animated:shouldAnimateLabels:completion:] + 224
	14  UIKit                               0x000000010665d169 -[UISwitch _handleLongPressNL:] + 452
	15  UIKit                               0x00000001067afe73 _UIGestureRecognizerSendTargetActions + 153
	16  UIKit                               0x00000001067ac4e5 _UIGestureRecognizerSendActions + 162
	17  UIKit                               0x00000001067aa4e2 -[UIGestureRecognizer _updateGestureWithEvent:buttonEvent:] + 843
	18  UIKit                               0x00000001067b29a0 ___UIGestureRecognizerUpdate_block_invoke904 + 79
	19  UIKit                               0x00000001067b283e _UIGestureRecognizerRemoveObjectsFromArrayAndApplyBlocks + 342
	20  UIKit                               0x00000001067a0101 _UIGestureRecognizerUpdate + 2634
	21  UIKit                               0x0000000106337f8a -[UIWindow _sendGesturesForEvent:] + 1137
	22  UIKit                               0x00000001063391c0 -[UIWindow sendEvent:] + 849
	23  UIKit                               0x00000001062e7b66 -[UIApplication sendEvent:] + 263
	24  UIKit                               0x00000001062c1d97 _UIApplicationHandleEventQueue + 6844
	25  CoreFoundation                      0x0000000105e45a31 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
	26  CoreFoundation                      0x0000000105e3b95c __CFRunLoopDoSources0 + 556
	27  CoreFoundation                      0x0000000105e3ae13 __CFRunLoopRun + 867
	28  CoreFoundation                      0x0000000105e3a828 CFRunLoopRunSpecific + 488
	29  GraphicsServices                    0x000000010970fad2 GSEventRunModal + 161
	30  UIKit                               0x00000001062c7610 UIApplicationMain + 171
	31  TableViewCrash                      0x000000010548e7ef main + 111
	32  libdyld.dylib                       0x000000010866d92d start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException