JsonPatchConflict error when duplicate identifier dicts exist

[symroe]

https://sentry.io/democracy-club-gp/ynr-v9/issues/840483333/?referrer=github_plugin

IndexError: list assignment index out of range
  File "site-packages/jsonpatch.py", line 402, in apply
    del subobj[part]

JsonPatchConflict: can't remove non-existent object '3'
(12 additional frame(s) were not displayed)
...
  File "candidates/models/needs_review.py", line 89, in needs_review_due_to_statement_edit
    for version_diff in la.person.version_diffs:
  File "people/models.py", line 457, in version_diffs
    return get_version_diffs(json.loads(versions))
  File "candidates/diffs.py", line 277, in get_version_diffs
    id_to_parent_ids[version_id], id_to_version
  File "candidates/diffs.py", line 276, in <listcomp>
    for parent_with_data in get_parents_version_data(
  File "candidates/diffs.py", line 222, in get_version_diff
    from_data = jsonpatch.apply_patch(from_data, [operation])

JsonPatchConflict: can't remove non-existent object '3'

[symroe]

This is a bug in JsonPatch that we'll have to work around until it's been fixed.

[symroe]

Fixed in #760