6.0.0: Rerunning an OpenCL fit with DREAM throws errors

[krzywon]

Describe the bug
A video showing how to reproduce the error.

To Reproduce
Steps to reproduce the behavior:

1. Run any fit with OpenCL enabled, and any optimizer other than DREAM.
2. Once the fit is complete, switch to the DREAM fitter and run the fit again.
3. Errors thrown and the fit tab will no longer run any fits with that particular model.

Expected behavior
The fit should run.

SasView version (please complete the following information):

• Version: v6.0.0

Operating system (please complete the following information):

• OS: Win10, MacOS (arm and x86)

[krzywon]

A few hours with @pkienzle and we have found the 2 underlying issues. The one seen by @wpotrzebowski in the posted video is due to a single fit parameter selected which causes a change in the covariance calculation. I have that fixed locally. The 2nd, OpenCL error, is because the OpenCL environment was being reset when any preference was being changed. I am working on a reliable fix for this one, but am nearly there. Expect a PR this afternoon (EST).