Duplicate roles causes error when adding a new account

This may just be a dev error, but here goes:

• I was adding a new article via the submissions, using a superuser account and putting in a new/unknown author as the author rather than 'myself'. And I received the following error on submitting the third form in the process (not added the article itself yet).
• [journal]/submit/13/authors/

Error Message

MultipleObjectsReturned at /submit/12/authors/

get() returned more than one Role -- it returned 2!

Request Method: | POST -- | -- http://localhost:8000/alpha/submit/12/authors/ 4.2.11 MultipleObjectsReturned get() returned more than one Role -- it returned 2! /Users/stephdriver/Documents/Janeway/venv/Janeway/lib/python3.9/site-packages/django/db/models/query.py, line 640, in get submission.decorators.submission_is_enabled_wrapper /Users/stephdriver/Documents/Janeway/venv/Janeway/bin/python3 3.9.19 ['/Users/stephdriver/Documents/Janeway/janeway/src', '/opt/homebrew/Cellar/python@3.9/3.9.19/Frameworks/Python.framework/Versions/3.9/lib/python39.zip', '/opt/homebrew/Cellar/python@3.9/3.9.19/Frameworks/Python.framework/Versions/3.9/lib/python3.9', '/opt/homebrew/Cellar/python@3.9/3.9.19/Frameworks/Python.framework/Versions/3.9/lib/python3.9/lib-dynload', '/Users/stephdriver/Documents/Janeway/venv/Janeway/lib/python3.9/site-packages', '/Users/stephdriver/Documents/Janeway/janeway/src/plugins'] Thu, 20 Jun 2024 08:41:29 +0100

details

https://dpaste.com/F2N2BXV9K

Start by reproducing the POST to /submit/12/authors/ with an unknown author and read the Django traceback around the Role lookup. Inspect how the submission authors step handles duplicate Role records. Done means the reported submission flow no longer raises MultipleObjectsReturned; the issue does not specify the intended duplicate-handling behavior.