[BUG] "Load calibration" followed by "Capture Background" gives error

[talonchandler]

"Load calibration" followed by "Capture Background" yields:
Error: unsupported operand type(s) for *: 'NoneType' and 'float'

[talonchandler]

It seems like the lca{a/b}_{0,60,120} attributes of QLIPP_Calibration are not being set correctly during "Load calibration".

Ziwen, would you mind helping out with this? I think you should be able to recreate this issue locally.

[talonchandler]

I think the return is used, but in a sneaky way by self.worker.returned here:

https://github.com/mehta-lab/recOrder/blob/main/recOrder/plugin/widget/main_widget.py#L2460

It seems like the calibration must be returned somehow, or else the LCs wouldn't receive any of the data from the thread.

This page was pretty helpful for me to understand how this section works:
https://napari.org/stable/guides/threading.html

"The @thread_worker decorator converts your function into one that returns a WorkerBase instance."