Describe the bug
No matter what the settings in the 3D LUT tab are set to prior to profiling, DisplayCAL will reset those settings to bt.1886 immediately after profiling. This is incorrect because when "Create 3D LUT after profiling" is checked, it should use the settings from the user rather than always using bt.1886.

I am working on fixing this bug in this branch, but my understanding of how DisplayCAL works is incomplete, so I would appreciate some help in finding a solution.

To Reproduce
Steps to reproduce the behavior:

1. input custom 3D LUT settings for pure power gamma 2.4
2. check "Create 3D LUT after profiling"
3. Profile with resolve patches over the net
4. After profiling, notice that the 3D LUT settings reset to bt.1886. This happened before the 3D LUT was automatically created.
5. If a comparison is needed, change the 3D LUT settings back to pure power gamma 2.4 and generate a new LUT without profiling, this is currently the only way to create a correct LUT.

Expected behavior
Profiling should not alter the user configuration.

Versions:

• OS: Mac OS 14.6.1
• Python Version: 3.9.14 and 3.12.4 (tested on both)
• ArgyllCMS Version: 3.3.0
• DisplayCAL Version: 3.9.14 and develop branch (tested on both)

Where to start
Look at my branch and the commits made so far. I think I found another related bug where if the offset level is changed without first setting custom gamma, the cfg values don't update, but I want someone to double-check my solution to that issue.

So far, all I've been able to figure out is that in display_cal.py, in the MainFrame() class, in update_controls(), the trc variable always returns None, meaning that the custom gamma code is never reached. Why this happens, I have not been able to figure out.

Additional context
This is the issue that caused #456