bug(scan): scan stuck in `pending` state when using 'empty' scan engine

[AnonymousWP]

Current Behavior

When I'm starting a scan with a custom scan engine that has all lines commented out, the scan's state remains 'pending' without returning an error whatsoever.

Expected Behavior

Do the absolutely necessary for a scan or either return an error, mentioning I should configure at least X, Y or Z within a custom scan.

Steps To Reproduce

1. Create custom scan engine
2. Comment out all lines
3. Start a scan with the custom scan engine

Environment

- reNgine: 2.2.1 and 2.3.0

Anything else?

Logs:

Details

celery-1       | initiate_scan                      | INFO | Engine ID: 17
celery-1       | initiate_scan                      | ERROR | 'NoneType' object has no attribute 'get'
celery-1       | Traceback (most recent call last):
celery-1       |   File "/home/rengine/rengine/reNgine/tasks/scan.py", line 82, in initiate_scan
celery-1       |     gf_patterns = config.get(GF_PATTERNS, [])
celery-1       |                   ^^^^^^^^^^
celery-1       | AttributeError: 'NoneType' object has no attribute 'get'

Screenshot:

Acknowledgements

• This issue is not a duplicate of an existing bug report.
• I have chosen an appropriate title.
• All requested information has been provided properly.