Cubeviz parser should accept SCI without ERR

[Jdaviz-Triage-Bot]

Reporter: pllim

As a user, when I have a gigantic cube and I don't really care about ERR showing in uncert-viewer. I should not be forced to load it just to make Cubeviz happy.

Two possible use cases:

1. A file with only PRIMARY and SCI extensions, no ERR.
2. A file with everything but I am only interested in SCI.

What I want to happen:

1. Cubeviz would just load it happily as-is. Shows SCI in flux-viewer and an empty uncert-viewer.
2. Cubeviz would let me provide an optional keyword telling it I just want the SCI extension.

What is currently happening:

1. Cubeviz throws an error complaining ERR is missing.
2. There is no way to do this.

Workaround? I tried loading the SCI (pf["SCI"].data) into a Spectrum1D object (giving it flux unit, mask, WCS myself). It would load without complaining about missing ERR but the loaded image is rotated 90 degrees, which is super annoying and out of scope of this ticket.

🐱

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DISCLAIMER: This issue was autocreated by the Jdaviz Issue Creation Bot on behalf of the reporter. If any information is incorrect, please contact Duy Nguyen