fix: ignore empty outputs in Tool node

[PedroGomes02]

Summary

Modify _extract_tool_response_text to avoid adding empty elements to the list. Handle only tool_response messages of types TEXT and LINK, ensuring no empty elements are created in the list for other types of messages.

Fixes #10987

Checklist

Important

Please review the checklist below before submitting your pull request.

• This change requires a documentation update, included: Dify Document
• I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.
• I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods

[laipz8200]

LGTM