Reproduction steps:
1. Open the attached project "BuggyUnscaledDeltaTime.zip"
2. Build and Run the Scene "SampleScene" to an iOS device
3. With the App running, turn off the device's screen
4. Wait a couple of hours
5. Turn the screen back on and observe the values of "Time.unscaledDeltaTime" at the top of the screen

Expected result: no values of 0 are returned
Actual result: multiple 0 values are being returned

Reproducible with: 2020.3.33f1
Not reproducible with: 2019.4.38f1, 2021.3.1f1, 2022.1.0f1, 2022.2.0a11

Reproduced with:
- iPhone 13 (iOS 15.0)

Notes:
- The time it takes to reproduce might vary, on iPhone 13 it takes ~2-3h for a single 0 value to appear, however, after ~5-6h 0 values are being constantly returned