Crashlytics错误报告-严重异常：NSInternalInconstanceException

我收到了Crashlytics的坠机报告。但我不明白坠机背后的主要原因是什么。

Fatal Exception: NSInternalInconsistencyException
-[UINSUIKitBackgroundingController _updateAppWideBackgroundStateSlammingNotifyingDelegate:]: Called off the main thread.

Fatal Exception: NSInternalInconsistencyException
0  CoreFoundation                 0x105194 (Missing UUID 1643f3d9704937e4b844c0c0a42bde3b)
1  libobjc.A.dylib                0x18e04 (Missing UUID 3d936842590331adb1ae1de4f4b448a6)
2  Foundation                     0x138e88 (Missing UUID 59ff845a05b23b64ae066ef1d6aee83e)
3  UIKitMacHelper                 0x6cc24 (Missing UUID e370286f589c3c77b4f4b8bd1bc9c595)
4  UIKitMacHelper                 0x6aff4 (Missing UUID e370286f589c3c77b4f4b8bd1bc9c595)
5  UIKitMacHelper                 0x3e7fc (Missing UUID e370286f589c3c77b4f4b8bd1bc9c595)
6  UIKitMacHelper                 0x24594 (Missing UUID e370286f589c3c77b4f4b8bd1bc9c595)
7  UIKitMacHelper                 0x249cc (Missing UUID e370286f589c3c77b4f4b8bd1bc9c595)
8  AppKit                         0x905914 (Missing UUID 07bc3607552a3eb9a9414911c589dbc5)
9  LaunchServices                 0x14af10 (Missing UUID f6ca2149ff2631a5bd0fb1e2e3d3482e)
10 LaunchServices                 0x14db80 (Missing UUID f6ca2149ff2631a5bd0fb1e2e3d3482e)
11 libdispatch.dylib              0x25f0 (Missing UUID 035d23d94cb5375990591f7878f89fee)
12 libdispatch.dylib              0x41b4 (Missing UUID 035d23d94cb5375990591f7878f89fee)
13 libdispatch.dylib              0xb8a8 (Missing UUID 035d23d94cb5375990591f7878f89fee)
14 libdispatch.dylib              0xc438 (Missing UUID 035d23d94cb5375990591f7878f89fee)
15 libdispatch.dylib              0x16c98 (Missing UUID 035d23d94cb5375990591f7878f89fee)
16 libsystem_pthread.dylib        0x3360 (Missing UUID f32ff902ba4330b0ad43a2a8a9ff69fe)
17 libsystem_pthread.dylib        0x2080 (Missing UUID f32ff902ba4330b0ad43a2a8a9ff69fe)

请有人帮忙找出问题所在。谢谢。