Reproduction steps:
1. Open the attached project “NullReference_Bug”
2. In the Project window select “Assets/Apoth/Test/TestingPingProb/New Test Ping Prop.asset”
3. Open the Console window
4. In the Inspector window, click the object reference of property “Prob 2” to ping the object in the Project window
5. Observe the Console window

Expected result: The referenced object gets pinged
Actual result: NullReferenceException console errors

Reproducible with: 2022.1.0b1, 2022.1.24f1, 2022.2.6f1, 2023.1.0b4, 2023.2.0a2
Not reproducible with: 2020.3.44f1, 2021.3.16f1, 2022.1.0a16

Reproducible on: Windows 10, macOS 13.1 Intel

Notes:
Make sure you do not change the Layout of the editor.
In some versions, the file needed to be selected in step 2 is called “DataFile.asset” instead