modify the truthiness check

[rozyczko]

Description

In the param_remap_to_sasmodels_convert method, the condition if not value: incorrectly treated the value 0.0 as false. When orientation parameters like theta or phi were set to 0, they were being replaced with np.nan, breaking subsequent fits.

Fixes #3053

How Has This Been Tested?

Local tests

Review Checklist:

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Documentation (check at least one)

• There is nothing that needs documenting
• Documentation changes are in this PR
• There is an issue open for the documentation (link?)

Installers

• There is a chance this will affect the installers, if so
  • Windows installer (GH artifact) has been tested (installed and worked)
  • MacOSX installer (GH artifact) has been tested (installed and worked)
  • Wheels installer (GH artifact) has been tested (installed and worked)

Licensing (untick if necessary)

• The introduced changes comply with SasView license (BSD 3-Clause)

[DrPaulSharp]

Very good spot here @rozyczko!

A couple of things from me, firstly, does this fix also need to be applied to the following lines dealing with the uncertainty and min/max values? It looks to me like they could trip on a zero value as well. Secondly, do you have an example of a bug that this branch fixes? I tried the instructions in #3053 but couldn't reproduce the bug there.

[krzywon]

This is a needed change, but I'm not seeing any improvement in the magnetic/2D fitting functionality. I think this should be merged, but don't think it fixes the underlying issue in #3053. I'll update the issue on recreating the problem later today.

[rozyczko]

The magnetic parameter values stored in MagnetismWidget.magnet_params were not being applied to the kernel_module before fitting. When only magnetic parameters were selected for fitting, the fitter used default sasmodels values instead of user-specified values. Including non-magnetic parameters worked because those triggered other code paths that updated the model correctly.

Added updateKernelModelWithExtraParams(model) call before fitting to ensure magnetic parameter values are synced to the kernel_module.

Added immediate sync to kernel_module when magnetic parameters are initialized.

Also, fixed typos in the polydisp widget.

[krzywon]

This seems to be working now! I get real errors and the magnetic params change as a part of the fit. Code looks good.

[krzywon]

@DrPaulSharp, when you are able, could you compare the behavior outlined in #3053 comment in both this branch and in main? I want to be sure others are able to see the difference in behavior before merging.

[DrPaulSharp]

Hi @krzywon I've tried this, and on this branch I do find that the values change on a fit, but the errors are still extremely large: