Crash on iPad when presenting as UIAlertControllerStyleActionSheet

[tasanobu-zz]

Crash Log

2015-07-17 12:28:09.187 Sample[75631:2123973] *** Terminating app due to uncaught exception 'NSGenericException', reason: 'Your application has presented a UIAlertController (<UIAlertController: 0x7fbcbd09b2e0>) of style UIAlertControllerStyleActionSheet. The modalPresentationStyle of a UIAlertController with this style is UIModalPresentationPopover. You must provide location information for this popover through the alert controller's popoverPresentationController. You must provide either a sourceView and sourceRect or a barButtonItem.  If this information is not known when you present the alert controller, you may provide it in the UIPopoverPresentationControllerDelegate method -prepareForPopoverPresentation.'
*** First throw call stack:
(
    0   CoreFoundation                      0x0000000107e98c65 __exceptionPreprocess + 165
    1   libobjc.A.dylib                     0x0000000109a03bb7 objc_exception_throw + 45
    2   UIKit                               0x0000000108e4b03a -[UIPopoverPresentationController presentationTransitionWillBegin] + 2650
    3   UIKit                               0x0000000108846d39 __71-[UIPresentationController _initViewHierarchyForPresentationSuperview:]_block_invoke + 1305
    4   UIKit                               0x0000000108845380 __56-[UIPresentationController runTransitionForCurrentState]_block_invoke + 189
    5   UIKit                               0x000000010875b5ec _applyBlockToCFArrayCopiedToStack + 314
    6   UIKit                               0x000000010875b466 _afterCACommitHandler + 533
    7   CoreFoundation                      0x0000000107dcbca7 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 23
    8   CoreFoundation                      0x0000000107dcbc00 __CFRunLoopDoObservers + 368
    9   CoreFoundation                      0x0000000107dc1a33 __CFRunLoopRun + 1123
    10  CoreFoundation                      0x0000000107dc1366 CFRunLoopRunSpecific + 470
    11  GraphicsServices                    0x000000010be9ea3e GSEventRunModal + 161
    12  UIKit                               0x00000001087378c0 UIApplicationMain + 1282
    13  Sample                              0x0000000107c88ef7 main + 135
    14  libdyld.dylib                       0x000000010a16b145 start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException

[tasanobu-zz]

Fix on v0.9.0