fix: handle S3 URIs with empty storage correctly

[knowsuchagency]

Summary

• Fixed parseS3Object function to properly handle S3 URIs with empty storage (s3:///)
• Empty storage strings are now converted to undefined instead of being passed as empty strings
• This prevents "Invalid path" errors in the backend when loading CSV previews and other S3 operations

Problem

When returning S3 objects from Python scripts using the format {"s3": path}, the system would auto-detect it as an S3 asset using the s3:/// prefix. However, this caused the parseS3Object function to return an empty string for storage, which led to backend validation errors.

Solution

Updated the parseS3Object function to check if the storage value is an empty string and convert it to undefined. This ensures the backend APIs receive the correct parameters and can handle S3 objects without explicit storage/bucket names.

Test Plan

Tested the parseS3Object function with various inputs:

• {"s3": "path/to/file.csv"} → works correctly
• {"s3": "path/to/file.csv", "storage": "mybucket"} → works correctly
• "s3:///path/to/file.csv" → now correctly returns undefined for storage
• "s3://mybucket/path/to/file.csv" → works correctly

Resolves #6442

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[!IMPORTANT] Fixes parseS3Object in utils.ts to handle S3 URIs with empty storage by converting empty storage strings to undefined, preventing backend errors.

• Behavior:
  • Fixes parseS3Object in utils.ts to handle S3 URIs with empty storage by converting empty storage strings to undefined.
  • Prevents "Invalid path" errors in backend for CSV previews and other S3 operations.
• Test Plan:
  • Tested parseS3Object with various inputs to ensure correct handling of empty storage in S3 URIs.

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[diegoimbert]

I don't understand how the fix changes anything, match?.[1] || undefined will return undefined if match?.[1] is falsy (and '' is falsy)

Also parseS3Object seems to only be used when opening an S3FilePicker so I don't see how it relates to backend validation

Note : this is why i used or (||) instead of nullish coallision (??)