[BUG] Gradescope crashing causes forward crash

[gregbell26]

Description

Issue

Gradescope crashes occasionally under periods of high load causing an empty entry in the submission metadata file.

When this the first entry in the list or in the submission sublist, the autograder crashes when finalizing the results metadata due to the missing score file.

Additionally, failed executions are counting against the student's submission limit.

Steps to recreate

Hard to reproduce: use example failed metadata instead

{
  "id": "REDACTED",
  "users": [
    "REDACTED"
  ],
  "created_at": "2024-11-12T22:51:05.537483-08:00",
  "assignment_id": null,
  "assignment": {
    "id": "REDACTED",
    "title": "Assessment 12: Image Compression",
    "release_date": "2024-11-04T14:00:00.000000-08:00",
    "due_date": "2024-11-12T22:59:00.000000-08:00",
    "total_points": "14.0",
    "course_id": "REDACTED",
    "group_submission": false,
    "group_size": null,
    "late_due_date": "2024-11-15T22:59:00.000000-08:00",
    "outline": [
      {
        "id": 39095172,
        "type": "ProgrammingQuestion",
        "title": "Autograder",
        "parent_id": null,
        "weight": "14.0",
        "content": [],
        "index": 1
      }
    ]
  },
  "submission_method": "upload",
  "previous_submissions": []
}

Results JSON should also be empty (or null)

Solution

In theory there are tests covering these cases, but it seems that they are missing some cases.
We also need to add an E2E test that verifies that we don't crash with a malformed results.json or submission_metadata.json.

Semi related to #87.

Acceptance Criteria

• Autograder no longer crashes when a student resubmits a failed autograder run.
• Autograder no longer crashes with a malformed submission_metadata.json or results.json
• Autograder no longer counts failed runs against student when computing submission limit.