why we get this content "{"role": "model", "parts": []}" in events table

[caichuanwang]

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Describe the bug
sometimes, we got this json data in filed 'content' in events table. Is this a error or result?

To Reproduce
Please share a minimal code and data to reproduce your problem.
Steps to reproduce the behavior:
It happens sporadically; I can't reproduce it.

Expected behavior
It is sporadic; once it occurs, the entire agent stops running.
The parts is empty list, and I do not know how to deal with it ? It means the running agent is finished or error?

Screenshots

Desktop (please complete the following information):

• OS: linux
• Python version(python -V): 3.12
• ADK version(pip show google-adk):1.14.0

Model Information:

• Are you using LiteLLM: Yes
• Which model is being used: gemini-2.5-flash

Additional context
Add any other context about the problem here.