[Recorded Future] handle exception raised when no attachment and no object_refs to report

[helene-nguyen]

Proposed changes

• handle case when no attachement found
• Add a fake ID in the report as STIX2 doesn’t allowed that a report have no object references and it raise an error when no object_refs exists and we still want to create the report ❌
• Solution preferred: Create a subclass of Report to have optional object_refs and not required

Related issues

• [RecordedFuture]: Exceptions observed during import of Analyst Notes #2938

Checklist

• I consider the submitted work as finished
• I tested the code for its functionality using different use cases
• I added/update the relevant documentation (either on github or on notion)
• Where necessary I refactored code to improve the overall quality

Further comments

[flavienSindou]

Great work!
Thank you for the detailed logs and the improvements regarding safer object access.