Reproduction steps:
1. Open the attached project "PushNotifCrash .zip"
2. Build and Deploy the project to an iOS Simulator
3. Put the App in the background
4. Open a macOS terminal window in "<Project Path>/Assets" and run the following command: "xcrun simctl push booted com.unity.pushncrash NotificationContent.apns"
5. In the Simulator window, press on the Notification

Reproducible with: 1.4.1 (2019.4.33f1), 1.4.2 (2019.4.33f1, 2020.3.23f1, 2021.2.4f1, 2022.1.0a16)
Could not test with: 1.3.2 (Errors are thrown in the Console)

Notes:
- Issue reproduces only when Notification is clicked while the App is in the background

First lines of the stack trace:
* thread #1, queue = 'com.apple.main-thread', stop reason = signal SIGABRT
frame #0: 0x00007fff6030992e libsystem_kernel.dylib`__pthread_kill + 10
frame #1: 0x00007fff603435bd libsystem_pthread.dylib`pthread_kill + 263
frame #2: 0x00007fff200fbcb5 libsystem_c.dylib`abort + 120
frame #3: 0x00007fff20254692 libc++abi.dylib`abort_message + 241
frame #4: 0x00007fff20245dfd libc++abi.dylib`demangling_terminate_handler() + 266
frame #5: 0x00007fff20179ace libobjc.A.dylib`_objc_terminate() + 96