`mrtest add` fails on pmaports!5520

While trying to apply pmaports!5520 (closed) to get the rear camera working on the Pixel 3a I have, I got this error:

Traceback (most recent call last):
  File "/home/user/git/mrhlpr/mrtest.py", line 9, in <module>
    mrtest.frontend.main()
  File "/home/user/git/mrhlpr/mrtest/frontend.py", line 85, in main
    mrtest.add_packages.add_packages(origin, args.mr_id, args.no_cache)
  File "/home/user/git/mrhlpr/mrtest/add_packages.py", line 120, in add_packages
    zip_path = mrhlpr.mr.get_artifacts_zip(mr_id, no_cache, origin)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/user/git/mrhlpr/mrhlpr/mr.py", line 173, in get_artifacts_zip
    pipeline_metadata = get_pipeline_metadata(mr_id, no_cache, origin)
                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/user/git/mrhlpr/mrhlpr/mr.py", line 141, in get_pipeline_metadata
    pipeline_id = api["pipeline"]["id"]
                  ~~~~~~~~~~~~~~~^^^^^^
TypeError: 'NoneType' object is not subscriptable

I initially had this problem when using the latest edge version of mrtest, but as you can see from the stacktrace the same error appears on the latest Git commit as well.