Fixed issue causing the quotient of vector subspaces to throw an exception when divisor is the zero space

[Noel-Roemmele]

Fixes #39507. Fixed issue where the quotient of vector spaces was throwing an error if the divisor was the zero space. Implemented the change suggested by Dave Morris on the initial bug fix request. Also added a doctest to ensure the bug is fixed.

📝 Checklist

• The title is concise and informative.
• The description explains in detail what this PR is about.
• I have linked a relevant issue or discussion.
• I have created tests covering the changes.
• I have updated the documentation and checked the documentation preview.

⌛ Dependencies

[github-actions]

Documentation preview for this PR (built with commit 0a9120d; changes) is ready! 🎉
This preview will update shortly after each push to this PR.

[DaveWitteMorris]

I think it would be better to have a slightly more comprehensive test, so I would suggest changing the dimension of V from 2 to 3. (And then A would be V.subspace([(1,0,0)]).)

Also, please put print(x) on a new line. Actually, I think it would be better (use less space) to just make a list of the elements, instead of printing them one per line, such as replacing the for loop with list(A/B).

And please merge the latest beta.

I could not reproduce the doctest failure in src/sage/coding/linear_code.py locally, so I don't think it is related to this PR, and I hope it will disappear when the CI runs on this branch again.

[Noel-Roemmele]

I've merged with the new beta and added the doctest changes Dave Morris suggested.

[DaveWitteMorris]

Oops, my mistake. I intended for A/B to be 2-dimensional so the doctest would be "slightly more comprehensive". So please change A to be the span of two vectors. To make it more interesting, they should probably not both be standard basis vectors, so perhaps V.subspace([(0,1,0), (1,1,1)]).

[Noel-Roemmele]

I've changed A to be the span of two vectors as suggested by Dave Morris.