Emulation Mode option gets disabled on entering Play mode in Holographic Emulation Window.

Steps to repro:
1. Create a new project.
2. File > Build Settings > UniversalWindows > Switch Platform.
3. Player Settings > XR Settings > Enable Virtual Reality Supported .
4. Add Windows Mixed Reality Supported SDK.
5. Windows > XR > Holographic Emulation > Enter in Play mode.
6. Exit from the Play mode.

Workaround:
Close the Holographic Emulation window and open again.

Actual Result:
Emulation Mode option gets disabled.

Expected Result:
The emulation Mode option is enabled.

Reproducible in:
2019.3.0a11, 2019.3.0a8, 2019.2.0f1.

Working Fine in:
2019.3.0a7.

Environment:
Only on Windows.