[Bug]: Passing invalid parameters to gemini throws Undefined array key "choices" /www/htdocs/vendor/openai-php/client/src/Responses/Chat/CreateResponse.php 54

Description

While testing gemini I noticed that passing invalid chat parameters doesn't throw the appropriate exception. It throws:

Undefined array key "choices" /www/htdocs/vendor/openai-php/client/src/Responses/Chat/CreateResponse.php 54

The reason the error isn't caught is because the error is returned as:

 array (
  0 =>
  array (
    'error' =>
    array (
      'code' => 400,
      'message' => 'Invalid JSON payload received. Unknown name "ddd": Cannot find field.',
      'status' => 'INVALID_ARGUMENT',
      'details' =>
      array (
        0 =>
        array (
          '@type' => 'type.googleapis.com/google.rpc.BadRequest',
          'fieldViolations' =>
          array (
            0 =>
            array (
              'description' => 'Invalid JSON payload received. Unknown name "ddd": Cannot find field.',
            ),
          ),
        ),
      ),
    ),
  ),
)

The HttpTransporter::throwIfJsonError() only checks for $response['error'], but in this case it's $response[0]['error'].

Steps To Reproduce

 $client  = \OpenAI::factory()
    ->withApiKey('YOUR-KEY')
    ->withBaseUri('https://generativelanguage.googleapis.com/v1beta/openai')
    ->make();
$result = $client->chat()->create($params = [
    'model' => 'gemini-2.5-flash',
    'messages' => [
        ['role' => 'system', 'content' => 'You can use tools if needed.'],
        ['role' => 'user', 'content' => 'Hello you.'],
    ],
    'ddd' => 'auto',
  ]);

OpenAI PHP Client Version

v0.16.1

PHP Version

8.2.5

Notes

No response

Start in HttpTransporter::throwIfJsonError() and inspect how the response is handled before CreateResponse.php accesses the choices key. Reproduce the invalid-parameter request against the Gemini base URI, then verify that the nested error response raises the appropriate exception instead of an undefined array-key error.