ios8.4 在聊天界面 双击home时崩溃

ios8.4在聊天界面双击home时崩溃，ios9没问题。applicationWillResignActive 崩溃地方是这个，崩溃日志
Thread 0 name:  Dispatch queue: com.apple.main-thread
Thread 0 Crashed:
0   libobjc.A.dylib                   0x000000019504bbd0 objc_msgSend + 16
1   CoreFoundation                    0x000000018330a2c0 __CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER__ + 16
2   CoreFoundation                    0x000000018324744c _CFXNotificationPost + 2056
3   Foundation                        0x0000000184176a7c -[NSNotificationCenter postNotificationName:object:userInfo:] + 68
4   UIKit                             0x0000000187e44a50 -[UIApplication _deactivateForReason:notify:] + 612
5   UIKit                             0x000000018807157c -[UIApplication _handleNonLaunchSpecificActions:forScene:withTransitionContext:] + 2604
6   UIKit                             0x0000000188067b80 -[UIApplication workspace:didReceiveActions:] + 124
7   FrontBoardServices                0x000000018bb993c4 __31-[FBSSerialQueue performAsync:]_block_invoke_2 + 28
8   CoreFoundation                    0x000000018331c278 __CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__ + 16
9   CoreFoundation                    0x000000018331b380 __CFRunLoopDoBlocks + 308
10  CoreFoundation                    0x00000001833199a4 __CFRunLoopRun + 1752
11  CoreFoundation                    0x00000001832452d0 CFRunLoopRunSpecific + 392
12  GraphicsServices                  0x000000018cc9b6f8 GSEventRunModal + 164
13  UIKit                             0x0000000187e42f3c UIApplicationMain + 1484
14  ttky                              0x00000001002bc9ac main (main.m:14)
15  libdyld.dylib                     0x00000001956e2a04 start + 0