Fix Exa blocks handling of empty results

[Swiftyos]

Summary

• ensure Exa search/contents/similar blocks return an error when API results are empty

Testing

• ruff check --fix autogpt_platform/backend/backend/blocks/exa/search.py autogpt_platform/backend/backend/blocks/exa/similar.py autogpt_platform/backend/backend/blocks/exa/contents.py
• black autogpt_platform/backend/backend/blocks/exa/search.py autogpt_platform/backend/backend/blocks/exa/similar.py autogpt_platform/backend/backend/blocks/exa/contents.py
• isort autogpt_platform/backend/backend/blocks/exa/search.py autogpt_platform/backend/backend/blocks/exa/similar.py autogpt_platform/backend/backend/blocks/exa/contents.py

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[qodo-merge-pro]

PR Reviewer Guide 🔍

Here are some key observations to aid the review process:

⏱️ Estimated effort to review: 1 🔵⚪⚪⚪⚪

🧪 No relevant tests

🔒 No security concerns identified

⚡ Recommended focus areas for review Error Message The error message "results are empty" is not very descriptive. Consider providing a more informative message that explains why empty results occurred or what the user should do next. yield "error", "results are empty" else:

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[deepsource-io]

Here's the code health analysis summary for commits 8f1b3eb..409d327. View details on DeepSource ↗.

Analysis Summary

Analyzer	Status	Summary	Link
JavaScript	✅ Success		View Check ↗
Python	✅ Success	❗ 3 occurences introduced	View Check ↗

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[Pwuts]

This doesn't fix error cases. I have a better fix for this :)

[Pwuts]

#10020