Requesting non existent keyword at index exceptions are thrown after restarting the editor on changing Graphics APIs to DirectX12 in HDRP project. It occurs only on first time.

Steps to repro:
1. Create anew HDRP Project.
2. File > Build Settings > Player Settings.
3. Other Settings > Uncheck "Auto-Graphics API for Window" checkbox.
4. Add DirectX12 > move to the top of the list > Restart the editor.

Actual Result:
Requesting non existent keyword at index exceptions are thrown.

Expected Result:
No exceptions are thrown in the console.

Reproducible in:
2019.3.0a9.

Working fine in:
2019.3.0a8, 2019.2.0b9.

Environment:
Only on Windows.