Error in handling Google Gemini API error responses – breaks OpenAI compatibility in openai-php/client

The community PHP client openai-php/client crashes with Undefined array key “choices” warning in CreateResponse.php when Gemini returns an error response (e.g., invalid parameters). Gemini’s error format differs from OpenAI’s (no “choices” key, different structure).

Issue reported in #692, fix available in open PR #693: https://github.com/openai-php/client/pull/693
(PR adds proper Gemini error handling, normalization, and tests.)