null values for queryParameters cause exception

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Description

In http_request.dart file, when we use dio to send requests, the queryParameters is null, and cause the exception

DioException [unknown]: null
Error: type 'Null' is not a subtype of type 'Object'

Expected behavior No exception.

Current behavior What happened.

Screenshots or Logs

<img width="966" height="443" alt="Image" src="https://github.com/user-attachments/assets/c3753580-c44c-44a7-9bd7-16e548a19a0a" />

Environment (please complete the following information):

• OS: [e.g. Debian GNU/Linux]
• Meilisearch version: [e.g. v.0.20.0]
• meilisearch-dart version: 0.17.0