How to reproduce:
1. Open the attached project or create a new one
2. Go to the File-> Build Settings-> Run in Xcode as Debug
3. Build for iOS and deploy the Xcode project to the iOS device
4. Open up the app switcher immediately on the black screen before the splash screen
5. Force quit the Player
6. Inspect the crash in the Xcode console
===Crash occurs===

Reproducible with: 2017.4.33f1, 2018.3.14f1, 2018.4.10f1, 2019.3.0b5, 2020.1.0a7

Reproducible with:
iPad Pro 12.9" (iOS 11.2.1)
iPad 5th generation (iOS 10.3.3)

Note: It was hard to figure out a way to pause the app right at the start-up, just keep pressing repeatedly the home button

First lines from the stack trace (see the full stack trace in the Edit section):
frame #0: 0x0000000102b35dcc wrukoladd`::lookup<core::basic_string<char, core::StringStorageDefault<char> > >() at hash_set.h:645:49 [opt]
frame #1: 0x0000000102b33d60 wrukoladd`::GetScriptingClass() [inlined] find at hash_map.h:185:23 [opt]
frame #2: 0x0000000102b33d58 wrukoladd`::GetScriptingClass() at MonoManager_Il2Cpp.cpp:173 [opt]
frame #3: 0x0000000102836234 wrukoladd`::InitializeCoreScriptingClasses() at CoreScriptingClasses.cpp:23:38 [opt]
frame #4: 0x00000001028361a8 wrukoladd`::GetCoreScriptingClassesPtr() at CoreScriptingClasses.cpp:2057:3 [opt]
frame #5: 0x0000000102835b1c wrukoladd`::Internal_ApplicationWantsToQuit() [inlined]