ID 502017 - Switching from Nuke color management to OCIO, then back again, sets the Viewer Process knob to None

Problem summary
Switching from Nuke color management to OCIO, then back again, sets the Viewer Process knob to None

Customer reported version
Nuke 13.0v5

Customer reported platform
macOS 11.6.1

Steps to reproduce

1) Open Nuke

2) Open the Project Settings by clicking Edit > Project Settings

3) Select the Color tab in the Project Settings window

4) Change color management from Nuke to OCIO

5) Change the color management option from OCIO to Nuke

6) The Viewer Process knob will display None

Expected behaviour
For the Viewer Process knob should display SRGB

Actual behaviour
The Viewer Process knob displays None

Workaround
Manually change the Viewer Process knob to SRGB

Reproduced by support
This bug has been reproduced in:
Nuke 13.1v2 - Windows 10 - macOS 10.15 - CentOS7
Nuke 13.0v5 - Windows 10
Nuke 12.0v1 - Windows 10
Nuke 11.0v1 - Windows 10
Nuke 10.0v1 - Windows 10
Nuke 9.0v1 - Windows 10 - macOS 10.15 - CentOS7

Earliest version tested
Nuke 9.0v1 - This issue appears to be in all versions of the product