Strange crash after entering the background?
<p>I got a few of these crashes (from Crashlytics), which I can't understand.</p>

<p>Anyone can understand what it is about?</p>

<p>I can see it happens after <code>applicationDidEnterBackground</code>. Does it mean it crashes after the app went into the background?</p>

<pre><code>Thread : Crashed: com.apple.main-thread
0  libobjc.A.dylib                0x181b9db90 objc_msgSend + 16
1  CoreFoundation                 0x1825314a4 -[_CFXNotificationRegistrar find:object:observer:enumerator:] + 1548
2  CoreFoundation                 0x182406788 _CFXNotificationPost + 368
3  Foundation                     0x182e0e89c -[NSNotificationCenter postNotificationName:object:userInfo:] + 68
4  UIKit                          0x18791f124 __47-[UIApplication _applicationDidEnterBackground]_block_invoke + 320
5  UIKit                          0x1879ef5e4 +[UIViewController _performWithoutDeferringTransitions:] + 128
6  UIKit                          0x18791ef90 -[UIApplication _applicationDidEnterBackground] + 100
7  UIKit                          0x18791f514 -[UIApplication _handleApplicationDeactivationWithScene:shouldForceExit:transitionContext:completion:] + 700
8  UIKit                          0x18792f990 -[UIApplication _handleApplicationLifecycleEventWithScene:transitionContext:completion:] + 448
9  UIKit                          0x18791961c __70-[UIApplication scene:didUpdateWithDiff:transitionContext:completion:]_block_invoke + 152
10 UIKit                          0x1879192a4 -[UIApplication scene:didUpdateWithDiff:transitionContext:completion:] + 712
11 FrontBoardServices             0x183ec77ac __FBSSERIALQUEUE_IS_CALLING_OUT_TO_A_BLOCK__ + 36
12 FrontBoardServices             0x183ec7618 -[FBSSerialQueue _performNext] + 168
13 FrontBoardServices             0x183ec79c8 -[FBSSerialQueue _performNextFromRunLoopSource] + 56
14 CoreFoundation                 0x1824dd124 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 24
15 CoreFoundation                 0x1824dcbb8 __CFRunLoopDoSources0 + 540
16 CoreFoundation                 0x1824da8b8 __CFRunLoopRun + 724
17 CoreFoundation                 0x182404d10 CFRunLoopRunSpecific + 384
18 GraphicsServices               0x183cec088 GSEventRunModal + 180
19 UIKit                          0x1876d9f70 UIApplicationMain + 204
20 Trenìt!                       0x1000f32e4 main (AppDelegate.swift:14)
21 libdispatch.dylib              0x181fa28b8 (Missing)
</code></pre>