ID 366325 - Colorspaces are incorrectly displayed with custom DefaultChannels.mtd files

Problem summary
Outside of Nuke-Default, Colorspaces are incorrectly displayed with custom DefaultChannels.mtd files 

Customer reported version

4.1v1

Customer reported platform
fedora

Steps to reproduce

1) Create a custom DefaultChannels.mtd file with recognisable entry adjustments such as below:

2) Set the OCIO environment variable to the ACES colorspace config, packaged with Mari:

3) Launch Mari and open the New Project dialog

4) Under the Channels tab, select your custom .mtd file

5) Notice that the Colorspace is not automatically filled out to match

Workaround
Unknown.

Reproduced by support
Reproduced by development, in-house.

Expected behaviour

Colorspace categories should be correctly read from the custom .mtd files irregardless of the colorspace config

Actual behaviour
When using a non nuke-default colorspace, such as ACES, the UI does not correctly display the options from the custom .mtd file and they are not always selected automatically.