fix(gemini): append empty choice to model response when there are no …

[sonald]

Title

make sure response has at least one choice

Relevant issues

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• [x] My PR's scope is as isolated as possible, it only solves 1 specific problem

Type

🐛 Bug Fix

Changes

gemini-2.5-pro-preview-03-25 at some cases will respond with a non-error message that has neither candidates nor promptFeedback, like this:

{
  "usageMetadata": {
    "promptTokenCount": 9291,
    "totalTokenCount": 9291,
    "promptTokensDetails": [
      {
        "modality": "TEXT",
        "tokenCount": 9291
      }
    ]
  },
  "modelVersion": "gemini-2.5-pro-preview-03-25"
}

this breaks apps like smolagents, this is a related issue on smolagents.

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Name	Status	Preview	Comments	Updated (UTC)
litellm	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Apr 22, 2025 7:40am

[krrishdholakia]

Hey @sonald can you add a unit test for this change in here

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All committers have signed the CLA.

[sonald]

@krrishdholakia I have added the test

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This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.