[Bug]: Conflicting compatibility checks

### What happened?

`test_message_stream_invalid_params` asserts that the response for a request with invalid parameters is a single Json RCP error response object (not a stream)
`test_tasks_resubscribe_nonexistent` asserts that it gets back a stream and that its first result is an error object

IMO (not sure about the spec) these two paths should yield the same type of response. Either a stream with a singular error object, or an error object alone.

### Code of Conduct

- [x] I agree to follow this project's Code of Conduct

Look at the two failing tests: test_message_stream_invalid_params and test_tasks_resubscribe_nonexistent. Understand the Json RCP spec regarding error responses for invalid parameters versus non-existent tasks. Compare the response types (single error object vs. stream with error) and decide which is correct. Modify the implementation to make both tests pass consistently.

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