我QLPreviewController用来预览图像和pdf文件。它适用于 iOS7-9。但是，当我点击 iOS9 设备上的共享按钮时，应用程序立即崩溃，但出现以下异常：
Fatal Exception: NSInvalidArgumentException *** -[__NSCFString rangeOfString:options:range:locale:]: nil argument
这不会发生在带有 iOS9 的模拟器上。我可以在 iOS7 和 8 设备上看到 AirDrop 共享菜单，但(null)描述顶部出现奇怪的标题。这是示例屏幕截图的链接，在带有 iOS7 的 iPhone 5 上拍摄：
你们有没有遇到过这样的问题？
来自 CrashLytics 的完整堆栈跟踪
Thread : Fatal Exception: NSInvalidArgumentException
0 CoreFoundation 0x00000001860a0f5c __exceptionPreprocess + 124
1 libobjc.A.dylib 0x000000019ac97f80 objc_exception_throw + 56
2 CoreFoundation 0x00000001860a0ea4 -[NSException initWithCoder:]
3 Foundation 0x0000000186efe598 -[NSString rangeOfString:options:range:locale:] + 348
4 Sharing 0x0000000195064118 -[SFAirDropActivityViewController attributedStringWithTitle:content:]
5 Sharing 0x00000001950633e0 -[SFAirDropActivityViewController viewDidLoad]
6 UIKit 0x000000018b5f7610 -[UIViewController loadViewIfRequired] + 1124
7 UIKit 0x000000018b5f7194 -[UIViewController view] + 28
8 UIKit 0x000000018bf3a244 __79-[_UIActivityGroupListViewController updateVisibleActivityGroupViewControllers]_block_invoke115 + 112
9 CoreFoundation 0x0000000185f9e6f0 __53-[__NSArrayI enumerateObjectsWithOptions:usingBlock:]_block_invoke + 100
10 CoreFoundation 0x0000000185f95418 -[__NSArrayI enumerateObjectsWithOptions:usingBlock:] + 148
11 UIKit 0x000000018bf39e90 -[_UIActivityGroupListViewController updateVisibleActivityGroupViewControllers] + 456
12 UIKit 0x000000018bf3a754 -[_UIActivityGroupListViewController viewDidLoad] + 720
13 UIKit 0x000000018b5f7610 -[UIViewController loadViewIfRequired] + 1124
14 UIKit 0x000000018b5f7194 -[UIViewController view] + 28
15 UIKit 0x000000018ba4901c -[UIAlertController setContentViewController:] + 284
16 UIKit 0x000000018b7f0278 -[UIActivityViewController viewDidLoad] + 1280
17 UIKit 0x000000018b5f7610 -[UIViewController loadViewIfRequired] + 1124
18 UIKit 0x000000018b5f7194 -[UIViewController view] + 28
19 UIKit 0x000000018b969bfc -[UIViewController _setPresentationController:] + 108
20 UIKit 0x000000018b962e58 -[UIViewController _presentViewController:modalSourceViewController:presentationController:animationController:interactionController:completion:] + 1328
21 UIKit 0x000000018b964840 -[UIViewController _presentViewController:withAnimationController:completion:] + 4428
22 UIKit 0x000000018b967278 -[UIViewController _performCoordinatedPresentOrDismiss:animated:] + 472
23 UIKit 0x000000018b6ee0a4 -[UIViewController presentViewController:animated:completion:] + 184
24 UIKit 0x000000018bc48c84 _UIDocumentInteractionControllerPresentPopoverFromItemOrShowActivityViewController + 356
25 UIKit 0x000000018bc48a70 -[UIDocumentInteractionController presentOptionsMenuFromBarButtonItem:animated:] + 264
26 QuickLook 0x000000018af9d220 -[QLPreviewController actionButtonTapped:] + 220
27 UIKit 0x000000018b62e3c8 -[UIApplication sendAction:to:from:forEvent:] + 100
28 UIKit 0x000000018b7ad3dc -[UIBarButtonItem(UIInternal) _sendAction:withEvent:] + 168
29 UIKit 0x000000018b62e3c8 -[UIApplication sendAction:to:from:forEvent:] + 100
30 UIKit 0x000000018b62e344 -[UIControl sendAction:to:forEvent:] + 80
31 UIKit 0x000000018b616c6c -[UIControl _sendActionsForEvents:withEvent:] + 416
32 UIKit 0x000000018b616db8 -[UIControl _sendActionsForEvents:withEvent:] + 748
33 UIKit 0x000000018b62dc5c -[UIControl touchesEnded:withEvent:] + 572
34 UIKit 0x000000018b62d88c -[UIWindow _sendTouchesForEvent:] + 804
35 UIKit 0x000000018b626ac0 -[UIWindow sendEvent:] + 784
36 UIKit 0x000000018b5f7a10 -[UIApplication sendEvent:] + 248
37 UIKit 0x000000018b5f5efc _UIApplicationHandleEventQueue + 5348
38 CoreFoundation 0x00000001860585a4 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 24
39 CoreFoundation 0x0000000186058038 __CFRunLoopDoSources0 + 540
40 CoreFoundation 0x0000000186055d38 __CFRunLoopRun + 724
41 CoreFoundation 0x0000000185f84dc0 CFRunLoopRunSpecific + 384
42 GraphicsServices 0x00000001910d8088 GSEventRunModal + 180
43 UIKit 0x000000018b65ef44 UIApplicationMain + 204