fix(upload.py): fix upload for local

[shah-siddd]

Pull Request

Summary

Fixes the 'NoneType' object is not a mapping error when uploading attachments (images, audio) with the Openlayer Python client against a local Openlayer deployment. Local presigned URLs omit S3 policy fields, but the client still passed None into **fields, causing the error.

Changes

• attachment_uploader.py: Handle presigned_response.fields is None
  • Use explicit is not None check and convert to {} when missing
  • Wrap dict(presigned_response.fields) in try/except for robustness
• upload_bytes_multipart: Guard against None when unpacking fields
  • Add fields = fields or {} so None is never used in **fields

Context

For local storage (OPENLAYER_BASE_URL=http://localhost:8080/v1), the presigned URL API returns url and storageUri but no fields. The client left fields as None, which led to **fields → **None and the 'NoneType' object is not a mapping error during multipart upload.

Testing

• Unit tests
• Manual testing (local Openlayer + test_openlayer_multimodel.py)
• Postman CI/CD
• Other (please specify)

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