fix: 🐛 brain (#2096)

fixed when brainful is empty

# Description

Please include a summary of the changes and the related issue. Please
also include relevant motivation and context.

## Checklist before requesting a review

Please delete options that are not relevant.

- [ ] My code follows the style guidelines of this project
- [ ] I have performed a self-review of my code
- [ ] I have commented hard-to-understand areas
- [ ] I have ideally added tests that prove my fix is effective or that
my feature works
- [ ] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged

## Screenshots (if appropriate):

backend/modules/chat/controller/chat/brainful_chat.py

@@ -143,6 +143,6 @@ def get_answer_generator(
                 prompt_id=prompt_id,
                 user_id=user_id,
                 metadata=metadata,
-                raw=brain_definition.raw,
-                jq_instructions=brain_definition.jq_instructions,
+                raw=(brain_definition.raw if brain_definition else None),
+                jq_instructions=(brain_definition.jq_instructions if brain_definition else None),
             )