How to reproduce:
1. Create a new project
2. Make sure your Project window is set to "One Column Layout" style
3. Enter and exit the Play Mode
4. Enter the Play Mode again
5. Select the Project window's search bar
6. Press the up or down arrow key
7. If no error appears exit and re-enter the Play Mode again until it starts appearing

Expected results: No errors are thrown
Actual results: The "NullReferenceException: Object reference not set to an instance of an object" error is thrown

Reproducible with: 2018.4.33f1, 2019.4.24f1, 2020.3.3f1, 2021.1.2f1, 2021.2.0a12

Notes:
- Only happens when the Project window is set to "One Column Layout"
- The error usually appears after entering the Play Mode for the second time but it's possible that it will start appearing after 3rd or 4th enter