How to reproduce:
1. Create a new 3D project
2. In the Package Manager install Universal RP and the new Input System (switch to it and restart when prompted)
3. Enter PlayMode

Expected result: The Editor doesn't throw any errors when in PlayMode
Actual result: The Editor is constantly throwing the following error: "You are trying to read Input using the UnityEngine.Input class, but you have switched active Input handling to Input System package in Player Settings."

Reproducible with: 2021.2.0a17, 2021.2.0a19
Not reproducible with: 2018.4.35f1, 2019.4.28f1, 2020.3.13f1, 2021.1.11f1, 2021.2.0a16

Notes:
1. Issue is caused by the "Standalone Input Module" on the "[Debug Updater]" GameObject created when in PlayMode
2. The issue only happens if the "Active Input Handling" option in the Player Settings is set to "Input System Package (New)"
3. Reproducible on both URP and HDRP
4. Doesn't seem to be dependant on the used URP (12.0.0) or Input System(1.0.2) package versions, since they're identical on both reproducible and not reproducible Editor versions
5. Reproducible on Ubuntu 18.04 and Windows 10