How to reproduce:
1. Create a new project in your preferred workspace and open it
2. Connect it to Perforce
3. Create a new material and submit it
4. Check out Its Asset Only again
5. Submit the material and observe the console

Expected result: no warnings are thrown / Editor does not try to submit .meta files for assets that only have their Asset file checked out
Actual result: ".meta file not opened on this client" warning is thrown

Reproduced in: 2020.1.0a6, 2019.3.0b5, 2019.2.7f2, 2018.4.10f1, 2017.4.32f1