fix: guard against empty choices and message=None in LLM response

[qizwiz]

Problem

In Co-creation-projects/JJason-DeepCastAgent/backend/src/services/script_generator.py, the LLM response is accessed without checking:

content = response.choices[0].message.content

This raises IndexError (empty choices) or AttributeError (message=None on filtered content).

Fix

if not response.choices or response.choices[0].message is None:
    raise ValueError("LLM returned empty or filtered response")
content = response.choices[0].message.content

2 lines added, 0 deleted.

Detected by pact static analysis.